Low-carb side effects
& 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.

The main solution to most common problems when starting low carb is to increase the intake of water and salt. It’s even better to do it preventatively during the first week. If you do, you’ll most likely not experience any of these problems, or they’ll only be minor.

Use one of the shortcuts below for specific problems – or just continue reading for all of them.

Top 6 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 most people experience during the first week, often on day 2-4. The “induction flu”, so called as it can mimic flu-like symptoms.

Headaches are very common during this transition, as is feeling tired, lethargic and unmotivated. Nausea is also common. It’s also possible to experience confusion or “brain fog” – feeling not smart at all. Finally, it’s common to feel irritable – perhaps most clearly experienced by the rest of your family.

The good news is that these symptoms usually disappear by themselves within a few days. The even-better news is that these symptoms can often be avoided altogether. The main cause is usually dehydration and/or salt deficiency, caused by a temporarily increased urine production.

The cure: water & salt

Salt & waterAny problems can be minimized, and sometimes entirely cured, by getting enough water and salt into your system.

For example try adding half a teaspoon of salt to a large glass of water. Drink it. This may reduce or eliminate side effects within 15-30 minutes. If so, this may be repeated once daily if needed during the first week.

A better-tasting option is to use broth or bouillon, e.g. chicken, beef or bone broth.

The bonus: more fat

Make sure to eat enough fat. Going low carb, low fat is a recipe for starvation and feeling hungry and tired. You should never endure hunger as you start on a low-carb diet. A proper low-carb diet contains enough fat to make you feel satiated and energetic. This can speed up the transition time and minimize the time spent feeling low when starting low carb.

So how do you get enough fat on low carb? There are any number of options, but when in doubt add butter to whatever you’re eating.

If necessary

If adding salt and water (and fat) does not completely eliminate the induction flu the best option is usually to just hang in there. Any remaining symptoms are likely to be resolved within days, as your body adapts to low carb and turns into a fat-burning machine.

If necessary, it’s of course possible to have some carbs and make the transition to low carb more gradual and slower. This is not recommended as a first option, as it slows down the process and makes the weight loss and health improvement less obvious immediately.

Learn more

Interview – Eric Westman Part 3
Do you want to know even more about how to get the maximum benefit and minimal side effects on low carb? Watch our five-part video course with Dr. Eric Westman on the membership site (free trial one month).

Avoiding transition problems like the induction flu is covered in part 3/5



Leg cramps

Leg cramps on a low-carb dietLeg 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. It’s a side effect of the loss of minerals, specifically magnesium, due to increased urination. Here’s how to avoid it:

  1. Drink plenty of fluid and get enough salt. This may reduce loss of magnesium and help prevent leg cramps.
  2. 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-Mag or Mag 64 a day for 20 days, then continue taking 1 tablet a day afterwards.
  3. If the steps above are not enough and the problem is bothersome, consider increasing your carb intake somewhat. This should eliminate the problem. The more carbs you eat though, the weaker the impact of the low-carb diet.



Constipation is another possible side effect, especially during the first time on a low-carb diet, as your digestive system may need time to adapt.

Constipation on a low-carb dietHere are the three steps to cure it, perhaps you only need the first one:

  1. Drink plenty of fluid and get enough salt. The most common cause of constipation on low carb is dehydration. This makes the body absorb more water from the colon and thus the contents get dryer, harder and constipation can result. The solution is to drink plenty of water and perhaps add some extra salt.
  2. Eat plenty of vegetables or another source of fiber. Getting enough good quality fiber from the diet keeps the intestines moving and reduces the risk of constipation. This can be more of a challenge on low carb where many sources of fiber are avoided, but eating plenty of non-starchy vegetables may solve this problem. Another, and completely carb-free, option for adding fiber to the diet is psyllium seed husks (can be dissolved in water).
  3. If the steps above are not enough, use Milk of Magnesia to relieve constipation. Amazon link


Bad breath

Bad breath on low carbOn a strict low-carb diet some people experience a characteristic smell from their breath, a fruity smell that often remind people of nail polish remover.

The smell is from acetone, a ketone body. This is a sign that your body is burning lots of fat and even converting lots of fat to ketones to fuel the brain. You are a fat-burning machine.

This smell can sometimes also turn up as body odor, especially if working out and sweating a lot.

Not everyone eating a ketogenic low-carb diet ever experience this ketone breath – and for most people who do it’s a temporary thing that goes away after a week or two. The body then adapts and stops “leaking” ketones through breath and sweat.

For some people it does not go away though, and it can be a problem. Here are the possible solutions. The first two are more general, the next three more targeted to the keto smell specifically.

  1. Drink enough fluid and get enough salt. If your mouth feels dry – and it often can when just 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.
  2. Maintain a 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 smells.
  3. Use a breath freshener regularly. This can mask the keto smell.
  4. Wait another week or two and hope for it to be temporary (most often it is).
  5. Reduce the degree of ketosis. If the smell is a long-term problem and you want to get rid of it, the easy way is to reduce the degree of ketosis. This means eating a bit more carbs, 50-70 grams per day is usually enough to get out of ketosis. Of course, this will reduce the effect of the low-carb diet when it comes to weight loss and diabetes etc., but for some people it can still be powerful enough. Another option is to eat 50-70 grams of carbs per day and add some intermittent fasting. This can get you roughly the same effect as a strict low-carb diet… without the smell.


Heart palpitations

Heart palpitations on a low-carb dietIt’s common to experience a slightly elevated heart rate during the first few weeks on low carb. It’s also common to experience that the heart is beating a bit harder. This is normal and usually nothing to worry about.

One common cause is dehydration and a lack of salt. A reduction in the amount of circulating fluid in the blood stream means that the heart will have to pump blood slightly harder or faster to maintain blood pressure.

The cure

The quick solution to this problem is to drink enough fluids and make sure to get enough salt.

If necessary

If adding salt and water does not completely eliminate heart palpitations, it can also be a result of stress hormones released to maintain blood sugar levels (if you’re on diabetes medication see section below). This is usually a temporary problem as the body adapts to a lower-carb diet. It should go away within a week or two.

In the uncommon situation that the problem persists – and the palpitations are bothersome to you – try to slightly increase the carb intake. This will reduce the effect of the low-carb diet somewhat, so it’s a trade-off.

Important note if on medication for diabetes or high blood pressure

Medical Alert


Avoiding the carbohydrates that raise your blood sugar decreases your need for medication to lower it. Taking the same dose of insulin as you did prior to adopting a low-carb diet might result in a low blood sugar. One of the main symptoms of this is heart palpitations.

You need to monitor your blood sugar frequently when starting this diet and adapt (lower) your medication. This should ideally be done with the assistance of a knowledgeable physician. If you’re healthy or a diabetic treated either by diet alone or just with Metformin there is no risk of hypoglycemia.

Learn more about Diabetes and Low Carb

High Blood Pressure

On a low-carb diet an elevated blood pressure tends to improve (normalize). This reduces 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 (here’s a good home monitor). If it’s low – e.g. under 110/70 – you should contact your doctor to discuss possibly reducing or discontinuing your blood pressure medication.

Learn more about blood pressure and low carb



Reduced physical performance

Reduced physical performance on low carbIn the first few weeks on a low-carb diet your physical performance can be severely reduced. There are two main reasons for this:

  1. Lack of fluid and salts. This cause of most early problems when starting low carb is a real killer when it comes to physical performance. Drinking a large glass of water with 0.5 teaspoons of salt 30–60 minutes before exercising is the solution, and can make a huge difference in performance.
  2. Adaptation to burning fat takes weeks. The second cause of reduced early performance is not as quickly fixed. It simply takes time for your body to shift from being a sugar-burner to burning primarily fat for energy, even in the muscles. It takes weeks or a few months. This adaptation will be faster the more you exercise while on a low carb, high fat diet. The end result has many benefits (see below).

Increasing physical performance on low carb

While transitioning to a low carb, high fat (LCHF) diet often reduces early physical performance, the long-term effect has many benefits. This is something that has only recently begun to be appreciated. In fact, a lot of elite athletes are now experimenting with LCHF diets and in some cases they are now crushing the competition.

The benefits of a LCHF diet in sports are mainly seen in long-distance running and other endurance events. The body’s fat stores are huge as opposed to the minuscule glycogen stores. This means that once fat-adapted, an athlete can perform for long periods of time without needing much (if any) external energy. This frees the athlete from having to activate his or her gastrointestinal organs during activity – a large amount of blood flow can instead be directed to the muscles. This also minimizes the risk of digestive issues during the activity.

Another benefit comes from the reduction of body fat usually seen on low carb. This reduction in body-fat percentage and lightening of your body is a huge bonus for most sports.

Watch Professor Stephen Phinney explain more about physical performance on low carb

Learn more

Do you want to learn much more about maximizing your physical performance on low carb? Then check out our interviews with several of the world’s leading experts on the topic, as well as the movie Run on Fat and people with their own experience to guide you:




Hair loss on low carb

Temporary hair loss

Temporary 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, meal replacements) but it can also occasionally happen on low-carb diets.

If so, it usually starts 3-6 months after starting a new diet, at which point you’ll notice an increasing amount of hairs falling out when brushing your hair.

The good news is that even if you should be so unfortunate this is only a temporary phenomenon. And only a percentage of your hair will fall out (the thinning will rarely be very noticeable to others).

After a few months, all the hair follicles will start to grow new hair, and when you have regrown your hair it will be as thick as before again. 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.

Every single hair strand on your head usually grows for about 2-3 years at a time. After that it stops growing for up to 3 months. Then a new hair strand starts growing in the same hair follicle, pushing the old hair out.

Thus, you’re losing hair every day, but as the hair strands are unsynchronized this is not so noticeable. You lose one hair and another starts growing, i.e. 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. This can happen for many reasons, like these:

  • Starvation, including calorie-restricted diets and meal replacements
  • Diseases
  • Unusually demanding exercise
  • Pregnancy
  • 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 3-6 months before the problem started – such as giving birth or transitioning to a strict low-carb diet – you don’t really have to do anything. In all likelihood the problem will be temporary.

As long as you eat a varied and nutritious low-carb diet it’s very unlikely that stopping it will speed up the hair regain, it will likely happen as quickly anyway. And unfortunately, you can’t stop the hair loss from happening once it has started, as the resting hairs will fall out whatever you do.

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, B12) it’s unlikely that they will show anything interesting.

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, most people never notice anything like it.

There are no studies on how to minimize this small risk, but it’s likely helpful not to restrict calories, i.e. don’t do a low-carb and low-fat diet (AKA “starvation”). Instead, eat as much fat as you need to feel satisfied and not hungry, an LCHF diet.

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 in general, and preferably don’t start an intense exercise program at the same time (wait at least a couple of weeks).



Elevated cholesterol

High cholesterol on a low-carb dietFirst the great news: A low-carb high-fat diet usually results in an improved cholesterol profile, indicating a lower risk of heart disease:

The classic effect of a low-carb diet on cholesterol is a slight elevation, partly due to an elevation of the good (HDL) cholesterol, indicating a lower risk of heart disease. This especially as the cholesterol profile also typically improves in two more ways: lower triglycerides and larger, fluffier LDL particles.

It has also been shown that two years with low-carb, high-fat diet advice results in reduced signs of atherosclerosis.

Potentially troubling cholesterol results

However, there are also potential problems, even if they are rare. On average, the elevation of total and LDL cholesterol is so small that most studies do not even pick up on it. But for a smaller number of people – possibly around 1-2 percent of the population – there can be worrying elevations of LDL and total cholesterol, beyond what can be considered normal. This potential risk is worth taking seriously. It can also be worth taking steps to correct it.

For example, a small subgroup of people, probably partly due to genetics, 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). This is not normal. Even if the lipid profile is otherwise good – with high HDL and low triglycerides – it may be unhealthy.

Looking closer at modern cholesterol tests in such cases there’s usually a high LDL particle count, and the apoB and apoB/A1 values are usually abnormally high. These numbers all indicate an increased risk of heart disease.

What to do

If you get a non-healthy lipid profile on a low-carb diet there are a few things to consider, in this order:

  1. Stop drinking Bulletproof coffee (butter, coconut fat or MCT oil in coffee). Don’t drink significant amounts of fat at all when you’re not hungry. This alone can often normalize cholesterol levels.
  2. Only eat when hungry and consider adding intermittent fasting (consistently reduces cholesterol levels).
  3. Consider using more unsaturated fats, like olive oil, fatty fish and avocados. Whether it will improve your health is unknown, but it will lower your cholesterol. And as it’s abnormally high that may be enough of a reason.
  4. Finally, if step 1-3 is not enough: Consider whether you really need to be on a strict LCHF diet for health reasons. If a more moderate or liberal diet (e.g. 50–100 grams of carbs per day) can still work for you, it will also likely lower your cholesterol. Just remember to choose good unprocessed carb sources (e.g. not wheat flour or refined sugar).

More details

LCHF and LDL – Dr. Sarah Hallberg
For more details about low carb and the percentage of people who get higher LDL cholesterol, watch this talk by Dr. Sarah Hallberg.

To statin or not to statin

Statin Nation
When cholesterol is high the question of cholesterol lowering medication, statins, is often discussed. These drugs do lower the risk of heart disease, but at the risk of very real side effects, like reduced energy, aching muscles, diabetes type 2 and a marginally reduced IQ.

As a general guideline, if you’re at high risk of heart disease, five years of taking a statin drug can reduce your risk of an heart attack by 1 percent and lengthen your life by about 3 days. Only you can decide whether that is worth the risk of side effects.

Please note that even these relatively small statistical benefits are a best-case scenario, as they are based on Big Pharma-funded studies.

It’s abundantly clear that effective lifestyle changes can have a far larger impact on your heart health than taking a statin drug. And without the side effects.

My cholesterol

FWIW, here are my cholesterol tests after 10 years on a low-carb, high-fat diet.



A low-carb diet and reduced alcohol tolerance

Low carb and alcohol tolerance

When on a strict low-carb diet most people need significantly less alcohol to get intoxicated. So be careful the first time you drink alcohol on low carb. Possibly, you only need half as many drinks as usual to enjoy yourself the most. Low carb will save you money at the bar.

The reasons 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 spare for burning alcohol, slowing down the process.

Alternatively, it could be because alcohol and sugar (fructose) is partly broken down in similar ways in the liver. Eating less sugar could thus make your liver temporarily less adapted 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:

Low-carb alcohol – the best and the worst drinks
Alcohol and the keto diet: 7 things you need to know



Gout and low carb

Gout and low carbIt’s often claimed that low-carb diets high in meat could cause gout. This is mostly wrong for two reasons:

  1. A low-carb diet should not be high in meat, only moderate.
  2. The risk of gout likely goes down on low carb, at least long term.

However, there may possibly be a slight increase in the risk of gout during the first few weeks on a strict low-carb diet.

For more on what really causes gout and how to avoid it, check out our full guide:

Gout and low carb



Improve this page

Do you have any suggestion – big or small – to improve this page? Anything that you’d like added or changed? Any other problems you’d like to see addressed? Comment below or e-mail me at andreas@dietdoctor.com.

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  1. Natasha
    Around two and a half weeks into my keto diet, I started feeling lightheaded on and off throughout the day. It has become a serious problem and I cannot find the reason behind it. I have now also developed the keto rash. I'm starting to wonder if this diet is right for me.

    please help!

    Thank you!

  2. Sean
    I supplement with magnesium and potassium ,which stop the cramps for me,
    Then I forget and they come back.
    I'm less worried about them now.
    Reply: #208
  4. Indie
    Hi Je
    I suffer the same symptoms- have you found an answer to this issue?
  5. 1 comment removed
  6. Jaake
    Serena, although ACV is an acid, I know many people who have CURED their acid reflux by using a regimen that includes ACV (and okay with juice/water). It seems counter-intuitive, but if you research why it works you'll understand.
  7. Jaake
    What was the ratio of "good" and "bad" cholesterol in your panel? That is important. The question of "high" cholesterol is by no means "settled" but the medical establishment just acts as though it is. I recommend you dig for more information about "high" cholesterol numbers and how good of an indicator they really are for cardio-vascular risk. (You have to dig hard, the internet is full of the common knowledge we all hear day in and day out.) Finally, after a lot of digging and having done (and am doing again, as a vegetarian) keto diet, I've come to learn a handful of things that work. EITHER LCHF (i.e. keto) will work to both lose weight, manage diabetes, and overall augment health--IF DONE CORRECTLY. To understand keto, you must realize that you are in a sense artificially shifting your metabolism the same way that "in nature" our primal ancestors would have done during periods of scarcity, or during the winter months when vegetation was minimal. Success with Keto begs the practitioner to become educated about nutrition and the human body, to do a certain amount of research--or get support that is very familiar with keto diet. Secondly, the opposite diet (for lack of a better descriptor) of low-fat whole foods plant based diet will ALSO work to lose weight and create great health. (There tends to be a battle of sorts that goes on between practitioners of the two... [they BOTH work]) Finally--in either case--or no matter what you eat or how you diet or don't diet--EVERYONE can benefit from practicing Intermittent Fasting. There are different ways of doing this. Intermittent fasting does not cost money--it saves money! Check it out. And, while it's not a diet, practicing some HIIT (high internsity interval training) type exercise is ALSO easy and convenient and DOES WONDERS. In all cases, if you can find a health professional/s to support you--all the better. Finding one who is knowledgeable in these areas---is a challenge, depending where you live.
  8. Jaake
    Donna, see my reply to comment #178 Becky. I wish you the best of luck, and do some research of your own. Try different things. Look into also incorporating intermittent fasting and high intensity interval training (easy, less time) as well... (-:
  9. Jasmine
    Hello, I am on a keto diet for one week, I am OK but I have one potential problem.
    Although I drink more than enough water (3-4 l per day) I do not go more than 3-4 times a day to urinate and there is very low amount of urine.
    Usually (before the keto diet) I was drinking the same amount of water and went to the toilet at least 10 - 12 times per day.
    What should I do? I hope that this will not cause some kidney problem in my case.
  10. simon
    i am addicted to coffee with condensed milk (4-5 cups a day), and love sweet stuff. I love carbs (rice, noodle, bread) and i exercise everyday 1-1.5hr, with a hard 15-16 min run of 2.4km. my weight was not going down despite getting fitter everyday. I decided to go on low carb diet (no rice, no noodle, no bread), no caffeine, no condensed milk. Within 1st 3 days, now, i suffering from all the side effects, induction flu (lethargic,irritability, lack of energy) , calf cramp when wake up, constipation, watery stools, bad breathe, reduced physical performances, .....what a archetypal case. I can still run as usual but normal activities i feel so lethargic, such as driving or basically walking in mall. However i treat this as "cold turkey" period, i need to go through, will persist. Any more tips to share from anyone?
  11. Rebecca Robb
    I started keto about 5 days ago, I started supplementing potassium and magnesium and I began to have chronic migraines so I stopped. Now I have strange aches in my chest. I went to the hospital last night and they said it's muscular. Could this be a deficiency with my magnesium/potassium/sodium? I do eat eggs/bacon/chicken/cheese/broccoli/beef burgers most day and cook everything in butter.
  12. 1 comment removed
  13. Dawn Lewis
    Hi I am a vegetarian, am I able to participate in this diet .. I eat fish and diary
    Reply: #214
  14. Peter Biörck Team Diet Doctor
    Hi Dawn Lewis!

    Yes you can participate. :)

    For members we have vegetarian meal plans.

    But if you don't want to join you can use our vegetarian recipes:

    Hi I am a vegetarian, am I able to participate in this diet .. I eat fish and diary

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