The keto flu,
other keto side effects,
and how to cure them
So you’ve just started a keto diet, and you feel poorly. You’re tired and you have a headache, you’re easily annoyed and have a hard time concentrating.
Congratulations, you have the keto flu. That’s what people call it, though it’s not really a flu, and it’s not contagious. It can just feel like a flu.
Most people feel some of these symptoms during the first week of a keto diet, especially day 3-5. Fortunately it’s temporary and you’ll feel fine again soon. Even better, there’s a simple fix1 that usually cures most or all of the symptoms in 15 minutes. Keep reading to find out!
Top 6 common issues on keto
There are several possible side effects on keto, not just the initial keto flu. Use the links below to learn more:
Less common keto issues
The keto flu
Symptoms of the keto flu:
- Difficulty focusing (“brain fog”)
- Lack of motivation
- Sugar cravings
The keto flu is caused by the transition when your body starts burning fat for energy instead of sugar.
This can be compensated for, effectively curing the keto flu.
The cure for the keto flu
The symptoms of the keto flu usually disappear by themselves within a few days, as the body adapts. But to get rid of them in 15 minutes, use this cure. The first step is by far the most important, and it’s often enough.
1. The cure: water & salt
Any 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 or twice daily, if needed, during the first week.
A better-tasting option is to drink a cup of broth or bouillon, e.g. chicken, beef or bone broth, once or twice a day.
2. The bonus: more fat
Step one above is usually enough. But if you still feel tired and not great, make sure to eat enough fat.
Going low carb, low fat is a recipe for starvation and feeling hungry and tired. You shouldn’t be hungry when you get started on a keto diet. A proper keto diet contains enough fat to make you feel satiated and energetic, especially after a meal. 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 keto? There are any number of options, but when in doubt, add butter to whatever you’re eating. Using our keto recipes is another great option.
3. If necessary: a bit more carbs
If adding salt and water (and fat) does not completely eliminate the keto 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 keto 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. But it can certainly remove any remaining symptoms of the keto flu.
Learn morefree trial one month).
Avoiding transition problems like the keto flu is covered in part 3/5
- Drink plenty of fluid and get enough salt. This may reduce loss of magnesium and help prevent leg cramps.
- 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.
- 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 benefits of the low-carb diet.
Here are the three steps to cure it, perhaps you only need the first one:
- Drink plenty of fluid and get enough salt. The most common cause of constipation on keto 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.
- 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 a keto diet 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).
- If the steps above are not enough, use Milk of Magnesia to relieve constipation. Amazon link
On a keto 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.
- 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.
- 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.
- Use a breath freshener regularly. This can mask the keto smell.
- Wait another week or two and hope for it to be temporary (most often it is).
- 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.
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 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, 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 keto 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 keto diet somewhat, so it’s a trade-off.
Important note if on medication for diabetes or high blood pressure
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 lower-carb keto 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.
High blood pressure
On a keto 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.
Reduced physical performance
In the first few weeks on a keto diet your physical performance can be severely reduced. There are two main reasons for this:
- Lack of fluid and salts. This cause of most early problems when starting keto 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.
- 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 keto
While transitioning to a keto 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 keto 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 keto. This reduction in body-fat percentage and lightening of your body is a huge bonus for most sports.
Do you want to learn much more about maximizing your physical performance on keto? 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:
Temporary hair loss on keto
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 a keto diet.
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
- 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 3-6 months before the problem started – such as giving birth or transitioning to a keto 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 keto 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 keto
First, temporary hair loss is relatively rare after starting a keto 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, a keto diet.
It may also be helpful to reduce other sources of stress during your first few weeks on keto. 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).
High cholesterol on a keto diet
First the great news: A low-carb high-fat diet usually results in an improved cholesterol profile, indicating a lower risk of heart disease:
- 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 classic effect of a keto 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 keto 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 keto diet there are a few things to consider, in this order:
- 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.
- Only eat when hungry and consider adding intermittent fasting (consistently reduces cholesterol levels).
- 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.
- Finally, if step 1-3 is not enough: Consider whether you really need to be on a keto diet for health reasons. If a more moderate or liberal low-carb 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).
To statin or not to statinaching 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.
Low carb and alcohol tolerance
When on a keto 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. Keto 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 keto. 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 keto alcohol guides:
Gout and keto
It’s often claimed that low-carb diets high in meat could cause gout. This is mostly wrong for two reasons:
- A keto low-carb diet should not be high in meat, only moderate.
- The risk of gout likely goes down on keto, at least long term.
However, there may possibly be a slight increase in the risk of gout during the first few weeks on a keto low-carb diet.
For more on what really causes gout and how to avoid it, check out our full guide:
More water and salt, see below… ↩