Low-carb and keto
& how to cure them
Are you struggling while starting out on a low-carb or keto diet? Do you get headaches, leg cramps, constipation or any of the other more common side effects? Use the information on this page to avoid them – and feel great while losing weight.
Use one of the shortcuts below for specific problems – or just continue reading for all of them.
Top 7 common problems when starting
Less common issues on low carb
Induction flu: Headaches, lethargy, nausea, confusion, brain fog, irritability
The most common side effect on low carb is what’s known as “induction flu,” so called because it can mimic flu-like symptoms. It commonly occurs during the first week or two, often starting on days 2 through 4.
Symptoms include headaches, feeling tired, lack of motivation, nausea and lethargy. It’s also possible to experience confusion or “brain fog.”3
The good news is that these symptoms often disappear spontaneously within a few days or at most a couple of weeks.
The even better news is that you can possibly avoid these symptoms altogether by consuming adequate water, salt, and fat on day 1.4 It is presumed that the main cause is usually dehydration and/or salt deficiency, caused by a temporary increase in urine production. Therefore, it makes sense that paying attention to hydration and electrolytes can help prevent it from occurring.
The cure: water & salt
You can potentially prevent, or at least minimize, many side effects by adding enough water and salt to replace what you lose when beginning a keto or low-carb diet.5
For example, increase your sodium intake by drinking a glass of water with half a teaspoon of salt. This may reduce or eliminate side effects within 15-30 minutes. If so, this may be repeated once or twice daily, if needed, during the first week.
A better-tasting option is to use bouillon or broth (chicken, beef, vegetable, or bone broth).
In addition to sodium, make sure you’re getting enough of two other important electrolytes, magnesium and potassium.
The bonus: more fat
When beginning a keto or low-carb diet, make sure to eat enough protein and fat.6Eating a diet that’s low in both fat and carbs is a recipe for feeling hungry, tired, and deprived.7 Low-carb diets should help you reduce your hunger, not increase it. A proper low-carb diet contains enough fat to make you feel satiated and energetic. This can help speed up the transition time and minimize side effects.
So, how do you get enough fat when eating low carb? There are a number of ways to eat more fat, but when in doubt, add butter to whatever you’re eating.
If adding salt, water, and fat doesn’t completely eliminate the induction flu, do your best to stick with it a bit longer. Any remaining symptoms are likely to improve within days, as your body adapts to low carb and begins using fat as its main fuel.
If necessary, it’s of course possible to include more carbs in order to have a more gradual transition to low carb. This is not recommended as a first option, as it may slow down the process and can result in slower weight loss and less dramatic health improvements.8
Leg cramps are not uncommon when starting a strict low-carb diet. It’s usually a minor issue if it occurs, but it can sometimes be painful.9 It’s unknown exactly why leg cramps occur, but they may possibly be due to the loss of minerals, specifically magnesium, due to increased urination.
Here’s how to avoid leg cramps:
- Drink plenty of fluid and get enough salt. This may potentially reduce loss of magnesium and help prevent leg cramps.10
- If needed, supplement with magnesium. Here’s a suggested dosage from the book The Art and Science of Low Carbohydrate Living by Drs. Jeff Volek and Stephen Phinney: Take 3 slow-release magnesium tablets like Slow-Mag11 or Mag 64 a day for 20 days, then continue taking 1 tablet a day afterwards.12
- If the steps above are not enough and the problem is bothersome, consider increasing your carb intake somewhat. This may eliminate the problem, although it may reduce the impact of the low-carb diet.
For even more information and tips, check out our full guide: Guide Here are the six key things to know to kick your leg cramps to the curb, in our full leg cramps guide.
Six ways to kick nasty leg cramps to the curb
Guide Here are the six key things to know to kick your leg cramps to the curb, in our full leg cramps guide.
Constipation is another possible side effect, especially when first starting a low-carb diet, as your digestive system may need time to adapt.13
Here are the three steps to cure it, and you may only need the first one:
- Drink plenty of fluid and get enough salt. One common cause of constipation on low carb may be dehydration.14 This makes the body absorb more water from the colon, so the contents get dryer and harder, leading to constipation. The solution? Drink plenty of water and perhaps add some extra salt.15
- Eat plenty of vegetables or another source of fiber. Getting enough dietary fiber keeps the intestines moving, which may reduce the risk of constipation. Some may find their fiber intake decreases when eating low carb. However, eating plenty of non-starchy vegetables plus some nuts may help solve this problem. Another option for adding fiber to the diet that’s nearly carb-free is psyllium seed husks (mixed with plenty of water) or ground flaxseed.16
- If the steps above are not enough, consider trying 2 to 4 tablespoons (30-60 ml) of Milk of Magnesia (magnesium hydroxide) to relieve constipation.1718
For more on constipation, check out the guide below. Guide Are you constipated since going low carb or keto? This guide will explain all-things related to constipation and low carb.
What to do about constipation on a low-carb or keto diet
Guide Are you constipated since going low carb or keto? This guide will explain all-things related to constipation and low carb.
On a strict low-carb diet some people experience a characteristic odor from their breath. It’s often described as a strong, fruity smell reminiscent of nail polish remover.
Higher levels of acetone can also lead to changes in body odor, especially when working out and sweating a lot.
Not everyone eating a ketogenic low-carb diet experiences this ketone breath – and for most people who do, it’s a temporary thing that often goes away after a week or two.21
For some people, it does not go away, though, and can remain a problem. Here are some possible solutions. The first two are more general, the next three more targeted to the keto odor specifically.
- Drink enough fluid and get enough salt. If your mouth feels dry – and it often can when starting a strict low-carb diet and getting into ketosis – this means you have less saliva to wash away bacteria. This can result in bad breath, so make sure to drink enough.
- Maintain good oral hygiene. Brushing your teeth twice a day won’t stop the fruity keto smell (that comes from your lungs), but at least it won’t be mixing with other odors.
- Use a breath freshener regularly. This can mask the keto smell.
- Wait another week or two and hope that it resolves. Clinical experience shows that it is a self-limiting side effect for many people. 22
- Reduce the degree of ketosis. If the smell is a long-term problem and you want to get rid of it, one solution is to get out of ketosis or greatly reduce the degree of ketosis. This means including a few more carbs in your diet. Eating 50-70 grams per day may be enough to get out of ketosis.23 Of course, this will likely reduce the effect of the low-carb diet when it comes to weight loss, diabetes, and other health benefits, but for some people, it may still be powerful enough. Another option is to eat 50-70 grams of carbs per day and add some intermittent fasting. This may help you achieve roughly the same effect as a strict low-carb diet, without the smell.24
It’s common to experience a slightly elevated heart rate during the first few weeks on low carb, along with feeling as though the heart is beating a bit harder. This is normal and usually nothing to worry about as long as there aren’t associated symptoms of chest pain, weakness or feeling faint.25
As with many other side effects, one common cause may be dehydration and a lack of salt.
The quick solution to this problem is to drink enough fluids and make sure to get enough salt.
If adding salt and water does not completely eliminate heart palpitations, your symptoms might be related to stress hormones being released to maintain blood sugar levels (if you’re on diabetes medication, see the section below).26 This is often a temporary problem that occurs as the body adapts to a lower-carb diet, and will likely go away within a week or two.27
In the uncommon situation that the problem persists – and the palpitations are bothersome to you – try to slightly increase your carb intake. This will reduce the effect of the low-carb diet somewhat, so it’s a trade-off.
It’s possible that supplementing with magnesium may decrease palpitations.28 Taking up to 400 mg of magnesium per day (the recommended dietary allowance, or RDA) is safe for people with normal kidney function.
Important note if on medication for diabetes or high blood pressure
Decreasing carbohydrates decreases your need for medication to lower blood sugar. Taking the same dose of insulin or other diabetes medication as you did prior to adopting a low-carb diet might result in low blood sugar. One of the main symptoms of this is heart palpitations.
You should monitor your blood sugar frequently when starting a low-carb diet and work with your doctor to safely reduce your medication. If you are healthy or have diabetes that is treated either by diet alone or just with metformin, there is less risk of hypoglycemia.
If you need help finding a doctor knowledgeable about low-carb diets, you can consult our clinician map.
High blood pressure
On a low-carb diet, elevated blood pressure tends to improve or normalize for most people.29 This can reduce the need for medication and your dosage may become too strong, leading to low blood pressure. One of the symptoms of this can be an increased pulse and heart palpitations. If you experience this, it’s wise to check your blood pressure and contact your doctor to discuss possibly reducing or discontinuing your blood pressure medication.
Reduced physical performance
In the first few weeks on a low-carb diet your physical performance can be severely reduced.30 There are two main reasons for this:
- Lack of fluid and salt. This cause of most early problems when starting low carb can really hinder physical performance. Drinking a large glass of water with 0.5 teaspoons of salt or a glass of broth 30–60 minutes before exercising might make a difference in performance.31
- Adaptation to burning fat takes weeks. The second cause of reduced early performance isn’t as quickly fixed. It simply takes time for your body to shift from burning sugar to burning primarily fat for energy, including your muscles.32 It can take weeks or even months. After the adaptation period, some may see significant benefits (see below).
Increasing physical performance on low carb
While transitioning to a low-carb, high-fat (LCHF) diet often reduces physical performance initially, it may provide several potential benefits long term.33
The benefits of a low-carb diet in sports may be more obvious in long-distance running and other endurance events. The body’s fat stores are significantly larger than its glycogen stores. This means that once fat-adapted, an athlete may be able to perform for long periods of time without needing much (if any) external energy. This frees the athlete from having to activate their gastrointestinal tract during activity and can minimize the risk of digestive issues.
Another benefit is the reduction of body fat that often occurs on low carb.34 This reduction in body-fat percentage and lightening of your body can be a bonus for many sports.
However, the science does not all agree that athletes benefit from going low carb. Two papers by Dr. Louise Burke showed a reduction in endurance race walking performance after 12-weeks of keto eating.35 Questions remain regarding if the adaptation period was long enough, but suffice it to say that this is still an area of debate without a clear answer.
Temporary hair lossTemporary hair loss can occur for many different reasons, including any big dietary change. This is especially common when severely restricting calories (e.g., starvation diets or meal replacements).36 But it can also occasionally happen on low-carb diets.37
If so, it usually begins 3 to 6 months after starting a new diet, at which point you’ll notice more hairs falling out when brushing your hair.
The good news is that even if you should be so unfortunate, this is usually a temporary phenomenon. And it’s likely that only a very small portion of your hair will fall out. Most find that the thinning will rarely be noticeable to others.38
After a few months, all the hair follicles will start to grow new hair and get back to normal. Of course, if you have long hair this could take a year or even more.
To understand exactly what is happening it’s necessary to know the basics of how hair grows.
Each hair on your head usually grows for about 3 to 5 years at a time. After that it stops growing for up to 2 months. Then a new hair strand starts growing in the same hair follicle, pushing the old hair out.39
So although you’re losing hair every day, because the hair strands are unsynchronized, this is not so noticeable. You lose one hair and another starts growing, so you always have about the same number of hair strands on your scalp.
Stress and synchronized hair loss
If your body experiences significant stress, more hair strands than usual can enter the resting phase at the same time.40 This can happen for many reasons, including:
- Starvation, including calorie-restricted diets and meal replacements
- Unusually demanding exercise
- Breast feeding
- Nutrient deficiencies
- Psychological stress
- Any big diet change
As the new hair strands start growing a few months later, all these formerly resting hair strands will drop at almost the same time. This is called “telogen effluvium” in fancy medical terms (read more about it), and it’s relatively common.
What to do
If there was an obvious triggering factor 3 to 6 months before the problem started – such as giving birth or transitioning to a strict low-carb diet – you don’t have to do anything. The problem should be temporary.
As long as you eat a varied and nutritious low-carb diet, it’s unlikely that stopping low carb will speed up hair regrowth. It will probably happen as quickly anyway. And unfortunately, you can’t stop the hair loss from happening once it has started, as the resting hairs will still fall out.
It’s possible to order blood tests for nutrient deficiencies, but unless you are on a vegetarian or vegan diet (with no supplements of iron or vitamin B12) it’s unlikely that these tests will show anything remarkable.41However, if you have prolonged hair loss despite consuming adequate calories, especially protein, and there is no other obvious reason, then you may want to check with your doctor to make sure there aren’t any rare medical conditions that may be causing the issue.
How to minimize the risk of hair loss when starting low carb
First, temporary hair loss is relatively rare after starting a low-carb diet.42
There are no studies on how to minimize this small risk, but it’s likely helpful not to restrict calories. For instance, don’t do a low-carb and low-fat diet (which your body may perceive as starvation). Instead, eat as much fat as you need to feel satisfied and not hungry.43
It may also be helpful to reduce other sources of stress during your first few weeks on low carb. Sleep well, be kind to yourself, and don’t start an intense exercise program at the same time (wait at least a couple of weeks).
First, the great news: A low-carb high-fat diet usually results in an improved lipid profile, suggesting a lower risk of heart disease:44
- New analysis: LCHF best for long-term weight and health markers
- New major study: a low-carb diet yet again best for both weight and health markers!
The typical effect of a low-carb diet is an increase in HDL cholesterol (often referred to as “good” cholesterol), and a reduction in triglycerides, indicating a potentially lower risk of heart disease. The cholesterol profile also typically fewer small, dense LDL particles.45
It has also been shown that low-carb, high-fat diet advice may result in reduced signs of atherosclerosis and an overall reduction in cardiovascular risk.46
Potentially troubling cholesterol results
However, there are also potential problems, even if they are not the norm. On average, the rise in total and LDL cholesterol is so small that many studies do not even pick up on it. But for a minority of people, there can be worrying elevations of LDL and total cholesterol, beyond what can be considered normal.47 This potential risk is worth taking seriously. It can also be worth taking steps to correct it.
For example, a small subgroup of people can end up with total cholesterol numbers over 400 mg/dl (10 mmol/l) on a strict low-carb diet, and LDL numbers over 250 mg/dl (6.5 mmol/l).48
While there are compelling theories that this could be physiologically appropriate and not dangerous, we do not have convincing data to prove safety. Therefore, we need to consider that even if the lipid profile is otherwise good – with high HDL and low triglycerides – it still may be unhealthy. We simply do not know for sure.
Looking closer at modern cholesterol tests in such cases, there’s usually a high LDL particle count, and the apoB and apoB/A1 values may be abnormally high. These numbers could all indicate a potentially increased risk of heart disease.
What to do
If you get a concerning lipid profile on a low-carb diet there are a few things to consider doing:
- Stop drinking Bulletproof coffee (butter, coconut fat or MCT oil in coffee). Don’t drink large amounts of saturated fat when you’re not hungry. This alone may normalize cholesterol levels.49
- Only eat when hungry and consider adding intermittent fasting which might reduce cholesterol levels in some cases.50
- Consider using more unsaturated fats, like olive oil, fatty fish and avocados. Whether it will improve your health is unknown, but it will probably lower your cholesterol.51 And since it’s abnormally high, that may be enough of a reason.
- If steps 1-3 are not enough: Consider whether you really need to be on a strict keto diet for health reasons. If a moderate or liberal low-carb diet can still work for you, it may also likely lower your cholesterol. Just remember to choose good unprocessed, high-fiber carb sources like vegetables, nuts, and seeds rather than wheat flour or refined sugar.
- Consult with your doctor: You should discuss with your healthcare provider if medication therapy is warranted.
For much more about low carb and cholesterol, see our full guide:
When cholesterol is high and especially for people with preexisting heart disease, the question of cholesterol-lowering medication, statins, is often discussed. These drugs have been shown to lower the risk of heart disease for some, but at the risk of side effects, like reduced energy, muscle pain and an increased risk of type 2 diabetes.
For people with preexisting heart disease, the relatively modest risk of side effects is often outweighed by the benefits. For people without heart disease, it’s often less clear.52 Discuss any change in medication with your doctor.
Low carb and alcohol tolerance
When eating a strict low-carb diet, people may need significantly less alcohol to get intoxicated.53 So be careful the first time you drink alcohol on low carb. Possibly, you’ll need half as many drinks as usual to get the same effect. Low carb may save you money at the bar.
The reason for this common experience is still unclear. It could be because the liver is busy producing ketones or glucose and thus has less capacity to metabolize alcohol, slowing down the process.
Alternatively, it could be because alcohol and sugar (fructose) are partly broken down in similar ways in the liver. So eating less sugar could temporarily reduce your liver’s ability to break down alcohol, just like drinking less alcohol would.
No matter the reason, you’ll likely tolerate less alcohol on low carb. Be prepared for it.
Obviously, if you’re going to be driving be extra careful. Don’t ever drink and drive, period.
For more, check out our two top low-carb and keto alcohol guides:
Gout and low carb
- A low-carb diet should not be high in meat, only moderate.54
- The risk of gout likely goes down on low carb, at least long term.55
However, there may possibly be a slight increase in the risk of gout during the first few weeks on a strict low-carb diet.56
For more on what really causes gout and how to avoid it, check out our full guide:
It’s been known for decades that when insulin levels drop — as they do when carb intake is very low— the kidneys excrete more sodium and water, although the exact mechanism isn’t clear:
Nutrition X 2019: Effects of differing levels of carbohydrate restriction on the achievement of nutritional ketosis, mood, and symptoms of carbohydrate withdrawal in healthy adults: A randomized clinical trial [randomized trial; moderate evidence] ↩
This piece of advice is based on theory and consistent experience from clinicians using it, and people testing it. [weak evidence]
There’s also some support from a study in which participants who were advised to drink bouillon experienced only minor side effects shortly after starting a low-carb diet:
Nutrition & Metabolism 2008: The effect of a low-carbohydrate, ketogenic diet versus a low-glycemic index diet on glycemic control in type 2 diabetes mellitus [randomized trial; moderate evidence] ↩
A low-carb diet is high in natural fats, including saturated fat. Although the issue remains somewhat controversial, several recent systematic reviews of randomized controlled trials and large observational studies have failed to show a connection between eating saturated fat and increased heart disease risk:
A systematic review of 14 trials found that eating very low carb appears to be more effective than more modest carb restriction for fat loss:
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This recommendation is from Drs. Volek and Phinney, who have conducted dozens of trials in people following very-low-carb diets. However, the intervention itself has not been tested in scientific trials. Therefore it is ungraded evidence without clear scientific backing other than expert opinion [weak evidence] ↩
In a study of people with type 2 diabetes who ate 20 or fewer grams of carbs per day, slightly more than half complained of constipation at some point during the trial:
Nutrition & Metabolism 2008: The effect of a low-carbohydrate, ketogenic diet versus a low-glycemic index diet on glycemic control in type 2 diabetes mellitus [randomized trial; moderate evidence]
Clinical Nutrition ESPEN 2019: Effect of flaxseed or psyllium vs. placebo on management of constipation, weight, glycemia, and lipids: a randomized trial in constipated patients with type 2 diabetes [moderate evidence]
Taking a standard dose of magnesium hydroxide is considered safe for people with normal kidney function and can be expected to produce a bowel movement within several hours:
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The three ketone bodies are acetone, acetoacetate, and beta-hydroxybutyrate. ↩
Breath ketone meters measure the amount of acetone in your breath in order to confirm that your body is burning fat and producing ketones:
Most studies on ketogenic diets limit carbs to less than 50 grams per day in order to promote nutritional ketosis:
Experienced clinicians have reported that patients are often unable to remain in ketosis when consistently eating more than 50 grams of carbs per day, although this may vary based on physical activity, fasting, and insulin sensitivity.[weak evidence]
While this hypothesis has not been specifically tested, the following studies demonstrate the beneficial effects of intermittent fasting
International Journal of Obesity 2011: The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomised trial in young overweight women [moderate evidence]
In one study, increasing magnesium intake by 50% helped reduce symptoms in people with frequent heart palpitations:
Journal of the American College of Cardiology 1997: Antiarrhythmic effects of increasing the daily intake of magnesium and potassium in patients with frequent ventricular arrhythmias [randomized trial; moderate evidence] ↩
This has been shown in several high-quality trials:
Nutrition Research 2019: Weight loss, improved physical performance, cognitive function, eating behavior, and metabolic profile in a 12-week ketogenic diet in obese adults [non-randomized trial; weak evidence]
This has been shown in both obese people and athletes:
Sports 2018: The three-month effects of a ketogenic diet on body composition, blood parameters, and performance metrics in CrossFit trainees: a pilot study [non-randomized trial; weak evidence]
Journal of Physiology 2017: Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers [randomized trial; moderate evidence]
PLoS ONE 2020: Crisis of confidence averted: Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible [randomized trial; moderate evidence]
Low-carb diets that contain both animal and plant foods typically provide adequate amounts of all vitamins and minerals:
In many low-carb studies showing health benefits, people are advised to eat a moderate amount of protein and as much fat as needed to feel satisfied:
Applied Physiology, Nutrition and Metabolism 2017: A 12-week low-carbohydrate, high-fat diet improves metabolic health outcomes over a control diet in a randomised controlled trial with overweight defence force personnel [moderate evidence]
Cardiovascular Diabetology 2018: Cardiovascular disease risk factor responses to a type 2 diabetes care model including nutritional ketosis induced by sustained carbohydrate restriction at 1 year: an open label, non-randomized, controlled study [nonrandomized study; weak evidence] ↩
Some studies suggest that smaller LDL particles are more correlated with heart risk compared to larger LDL particles:
Cardiovascular Diabetology 2018: Cardiovascular disease risk factor responses to a type 2 diabetes care model including nutritional ketosis induced by sustained carbohydrate restriction at 1 year: an open label, non-randomized, controlled study [non-controlled study; weak evidence] ↩
In studies, some people eating low-carb diets have experienced a 30-44% increase in LDL cholesterol:
Sports 2018: The three-month effects of a ketogenic diet on body composition, blood parameters, and performance metrics in CrossFit trainees: a pilot study [non-randomized trial; weak evidence] ↩
Consuming a lot of saturated fat has been shown to increase the number of LDL particles in some people:
The American Journal of Clinical Nutrition: Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults [randomized trial; moderate evidence]
A study in people with metabolic syndrome found that consuming fish oil and olive oil for 3 months significantly lowered their LDL cholesterol levels:
A 2017 review of the evidence of statin use in primary prevention showed that after 5 years, no lives were saved by statins and 1 in 104 people were prevented from having a heart attack, while 1 in 50 developed diabetes and 1 in 10 developed muscle damageThennt.com 2017: Statin drugs given for 5 years for heart disease prevention (without known heart disease) [overview article; ungraded] ↩
This is commonly reported by people on a keto diet. However, there isn’t much scientific research yet to explain why tolerance seems to be reduced, just theories:
In a randomized trial of people who ate a high-protein, low-carb diet for six months, uric acid levels declined, especially in those who were obese:
This RCT showed that a low carb diet led to the same amount of uric acid reduction as did a low-fat or a Mediterranean diet
Diabetes Care 2000: Effects of Low-Fat, Mediterranean, or Low-Carbohydrate Weight Loss Diets on Serum Urate and Cardiometabolic Risk Factors: A Secondary Analysis of the Dietary Intervention Randomized Controlled Trial (DIRECT) [randomized trial; moderate evidence]
There’s also some interesting early research suggesting that a ketogenic diet may help reduce gout flares, although much more study is needed:
In the following nonrandomized study, a 30% protein diet led to lower uric acid levels and fewer gout attacks
Annals of Rheumatologic Diseases 2000: Beneficial effects of weight loss associated with moderate calorie/carbohydrate restriction, and increased proportional intake of protein and unsaturated fat on serum urate and lipoprotein levels in gout: a pilot study [nonrandomized study, weak evidence]
Most studies have found no differences in uric acid levels among people on low-carb diets vs. low-fat or control diets:
Diabetes Metabolism Research & Reviews 2018: Effect of low-carbohydrate diet on markers of renal function in patients with type 2 diabetes: a meta-analysis
[systematic review of randomized trials; strong evidence]
Yet some low-carb researchers and clinicians have reported that some people who start eating low-carb diets experience an initial temporary rise in uric acid levels that could potentially slightly increase gout risk. [weak evidence]