Side-Effects of the Ketogenic Diet: Are They Dangerous?

Are There Side-Effects to the Keto Diet?
Is It Safe?

side effects

You’ve heard the saying “No Pain, No Gain” when it comes to achieving goals in the gym. The same saying can also be used for effective diets, in that you won’t be able to achieve physical and mental health goals without putting in the effort and giving up on many of the nice things in life.

When it comes to the keto diet, it’s no different, and every diet that makes drastic changes for the positive will result in some side effects as your body adapts. The types of side effects can vary from person to person and depend on a lot of different factors about your health and lifestyle.

If you’ve already heard about some of the side-effects that come with this special diet and are starting to freak out, don’t panic. We’re going to break down everything you need to know when it comes to what your body will experience when using these weight loss products for the first time.

Is It Safe To Do The Keto Diet?

man having a headache

The keto diet is safe as long as you stick to specific guidelines and make sure you don’t starve your body of vital nutrients. While the side effects listed on this page are common, they are linked to your body’s metabolism making some drastic changes.

Just like going to the gym for the first couple of times after a lazy absence will cause a lot of sore muscles and stiffness, removing certain things from your diet will require some time to adjust.

You will also see a lot of reports that highlight risks of a keto diet, but these generally lack a lot of insight into the reasons why many people seem to suffer from a lot of side effects.

We won’t butter it up and wrap it in a bow to tell you that it’s going to be an easy time. You should seriously question any diet that makes such promises.

Instead, we aim to present you with all the information you need to make sure you reduce side effects to a minimum. Understanding the negatives that you might encounter and why they happen will help you to avoid them altogether.

And with the right meal plan and supplements, you can avoid most of these altogether.

First though, let’s take a look at what might happen.

What Side-Effects Can We Expect From Ketosis?

side effects

There are several side effects that can be experienced on the path to ketosis, including flu like symptoms, heachaches, diarrhea, constipation, reduced energy and brain fog.
However, it’s important to remember that not everyone experiences ketogenic diet side-effects when starting this new lifestyle and thankfully, the symptoms are all temporary and can pass very quickly. 

These problems vary with every individual, but just to make sure that all your bases are covered, we’re going to break down every possible keto side effect that you can ever experience.

1. Flu Symptoms

Lady with flu

Within the first 2-4 days of beginning this lifestyle change, you might get a common keto diet side-effect known as the “keto flu” or “induction flu” because it has flu-like symptoms.

This means that you might experience:

  • Headaches
  • Lethargy
  • Lack of motivation
  • check
    Brain fog or confusion
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Although these symptoms typically go away completely within a few days, they are also completely avoidable if you stay very hydrated and increase your sodium intake. It also helps to make sure you're eating enough healthy fats.

2. Dizziness & Drowsiness

man sitting and holding head

As you dump water while on the diet, you're going to be losing minerals such as sodium, potassium and magnesium.

Having lower levels of these minerals in your body will make you feel tired, lightheaded or dizzy.

You may also experience leg crampsheadaches and skin itchiness.

Fatigue and dizziness are the most common ketogenic diet side-effects  common ketogenic diet side-effects when you're on the diet and they can be avoided for the most part by making sure you stay ahead of mineral loss. You can do this by eating or sipping more salty things throughout the day. You can also eat potassium-rich foods. Green leafy vegetables, dairy, and avocados are high in potassium and are a good place to start.

3. Low Blood Sugar

block on sugar on spoon

For most people, adapting to this process can be hard because they're used to eating a higher carb meal.

Your body is used to putting out a certain amount of insulin to take care of the sugar that gets created from all that carbohydrate intake.

When you suddenly drop your carbs on this special meal plan, you may have some transient low blood sugar episodes that will feel very scary.

Just remember to not freak out.  If this happens, it's okay to increase your carb intake in the beginning stages to allow your body to level out and adapt easier. If you do happen to go on a cheat session, make sure to quickly take an exogenous ketones supplement afterward to make sure you don't get knocked out of ketosis.

4. Sleep Issues

man can't sleep

Some people say that they find it hard to sleep when on the lifestyle.

This may be an indication that insulin and serotonin levels are low.

You could try this little trick: eat a snack which contains both protein and carbohydrates right before bed. 

The carbohydrate will increase insulin levels, which will allow more tryptophan from the protein to get into your brain, which will then allow you to sleep easier.

5. Frequent Urination

a constipated boy

After the first day, you'll probably notice that your body will force you to urinate more often.

This is due to the fact that your body is burning up the extra glycogen in your liver and muscles.

We know that breaking down glycogen releases a lot of water, so as your carb consumption and glycogen stores drop, your kidneys will start dumping this excess water. This is one of the very common side effects of the keto diet.

Also, as your circulating insulin levels drop, your kidneys will start excreting excess sodium, which will also cause more frequent urination.

6. Constipation


This is another one of the most common ketogenic diet side-effects and is usually a combination of dehydration, sodium loss, overeating of dairy or nuts, or even possibly magnesium imbalances.

If 400 mg of magnesium citrate isn't helping, you may want to cut back on your dairy consumption to rebalance your calcium intake to your magnesium intake.  

You will also do good to drink more water and cut back on the nuts you're eating.

7. Diarrhea

man suffering from diarrhea

This side-effect of the ketogenic diet is not unusual and should resolve itself over a few days.

Diarrhea can happen just because of the change in routine, or if an unwise decision is made to also limit fat consumption on a low-carb meal plan, which results in eating too much protein.

Make sure you replace the carbs you are cutting with more fat; preferably with  saturated fat such as butter, coconut oil, or  MCT oil to avoid these ketosis side effects.

8. Muscular Cramps

man experiencing leg cramps

Loss of minerals when first starting the keto diet can cause muscle cramps, especially leg cramps, in some people.

Similar to the other keto diet side-effects we’ve mentioned, drinking lots of water and eating things that have sodium can help prevent cramps and reduce mineral loss.

9. Smelly Breath

Man Blowing in Baby Face

If you’re on this diet or have been on it before, you are probably aware that as the body starts to metabolize fat, being in the state of ketosis can actually cause dry mouth and poor breath.

There is nothing one can do about this ketogenic diet side-effect; it’s just the nature of the beast. 

Unfortunately, this can also arise when using certain products, but it’s not  as lasting when you're on this type of diet. Chewing gum or mints is about the best option for you if it becomes a noticeable issue. Bad breath may be caused by over-consumption of some certain weight loss products, so tailoring the quantity of your consumption of those products may prevent excess BHB from being converted to acetone (which is likely excreted by the lungs, thereby causing your breath to smell bad).

10. Health Palpitations

diagnosis palpitations

You might notice a slight increase in heart rate in the first few weeks of eating a lower amount of carbs. This is probably common in those who usually have low blood pressure.

It’s often just due to a lack of sodium and water, causing a reduction in the fluid circulating in the blood.

This may then cause the heart to pump slightly faster or harder. So again, drink, drink, drink water, and add more sodium to your  food. This problem should go away within a week or two, but if you need to lessen the time that it takes, then you can slightly increase your carb intake.

You might also want to consider a high-quality multivitamin containing zinc, selenium, and magnesium to replace any nutrients lost during adaptation and to avoid any more side-effects from keto.

11. Brain Fog

man experiencing brain fog

For people who do not know what "brain fog" is, let me tell you this: it's not fun.

It's when you get forgetful, can't think properly, and can't even communicate correctly.

I can remember it happening to me once. I forgot how to go to some place that I've gone to a million times, and I can definitely say that it's really weird. 

The best description that I can give to it is something like "mental fatigue." There are some cases of people reporting to having experienced "keto brain fog" while on the diet. However, upon digging through those reports, I can say that there's a chance it could be caused by something else as well.

There are health conditions that become more intense when you're are on a completely different routine, which means that your body is trying to adapt to something new. This might be the one that's causing some of these ketosis side-effects.

This is why we always tell people to consult a doctor first before committing to a whole new lifestyle like the ketogenic diet. Also, there hasn't been any confirmation that being on the lifestyle can cause keto brain fog. In fact, there is research to support the notion that brain fog can potentially be alleviated by using most keto supplements. Dr. Bill Lagakos has caused quite a stir upon releasing his research on the matter. 

12. Reduced Athletic Performance

Athletic Abilities

This is one side effect to be very aware of if you spend a lot of time in the gym or doing any kind of high-performance sport.

During the initial stages after making your dietary changes, it will take time for your metabolism to adjust.

Switching from blood glucose to ketone as an energy source doesn’t happen overnight. During this time of adjustment, you will feel drained, tired and generally lacking energy. 

If you then hit the gym to squat or bench press the same weights as before, you will likely struggle, and this can be a safety concern.

The best thing to do is take it easy with your exercise for the first couple of weeks of keto.

13. Irritability

irritated man

If you’ve ever tried out diets and haven’t become irritable, then you’ve probably been doing things wrong. Let’s face it, who has ever felt hungry and was happy about it.

The same is going to be the case when you make keto lifestyle changes, as your body will interpret the initial sudden change as a sign of starvation. 

This releases many hormones, some related to stress, and they can make you feel on edge.

However, there are ways to deal with all side effects by making adjustments and taking supplements.

Make sure you keep an eye on your mood, as you don’t want to annoy people around you whose support you might need.

Less Common Side Effects

1. Keto Rash
This is quite rare, but you could notice a reddening of the skin that tends to be a bit itchy. In most cases, this can be the result of a food allergy, as you will significantly change the type of food you eat.

2. Blurred Vision
With low energy levels at the initial stages, your vision can become blurred. Pay close attention to this, as you don’t want it to put you in danger.

3. Hair Loss
One of the leading causes of hair loss is a lack of vitamins and minerals. Make sure you top up your diet with some supplements to avoid such issues.

4. Gout
During the first few weeks of making this lifestyle change, you can encounter inflammation of the joints in the toes. High levels of meat in your diet and an increase in uric acid are common with keto, which can trigger temporary gout.

5. Gallstone Problems
Generally speaking, gallstones are more common on high-carb-low-fat diets as less bile is needed to digest carbs. With keto doing the opposite, more bile is required which means less stays in the gall bladder where it can crystallize.

6. Elevated Cholesterol Levels
This is indeed a concern if you go very heavy on meat and dairy products. It’s not easy to get all the balances right, but you should look at lean cuts of meat, and switch to more fish and seafood.

7. Higher Fasting Blood Glucose
Even after months of sticking to a strict plan, you can measure high glucose levels first thing in the morning. These then generally decline throughout the day, even after eating. This will only be a concern if insulin levels are low as well.

8. Dangers When Breastfeeding
During breastfeeding periods it is not advisable to start an extremely low carb diet. If you have been doing it for months successfully and have no side effects, then continuing with your diet as is.

9. Insomnia
When you're getting into ketosis, it is quite possible to have issues when sleeping. Some people call this "keto insomnia". Don't worry, it goes away really quickly as long as you stay true to your diet. 

Frequently Asked Questions

Is Ketosis Hard On The Kidneys?
Ketosis is not harmful to your kidneys with several studies showing that quite the opposite is the case. What can contribute to kidney failure is ketoacidosis, which is a combination of high ketone and glucose levels. And this is something that generally only affects diabetics.

Is Ketosis Bad For Your Liver?
Following a strict keto diet doesn’t cause health concerns for your liver. As with all diets, it’s about getting the balance right, and the main reason that you could develop fatty deposits in the liver is a lack of low carb vegetables and fiber.
As always, every type of diet can cause problems if it doesn’t balance all your nutritional needs.

Is The Keto Diet Safe Long Term?
The keto diet is perfectly safe and suitable as a long term lifestyle choice. Once you overcome some of the initial side effects and you adapt your daily routines, it’s a great way to keep weight off and maintain overall better health.

Is The Ketogenic Diet Bad For Your Heart?
Generally speaking, keto is safe for your heart. Several studies have even proven that it leads to lower blood pressure and reduced triglycerides, which are positive for cardiac health.
However, if you do have underlying heart issues, then a conversation with your doctor is advised.

Is It Bad For Your Cholesterol?
Sticking to a strict keto diet plan will not increase your cholesterol to spike. The main reason that people see increased levels is when a wrong balance of meat and dairy products is introduced. Eating more fish and seafood is an excellent way to remove cholesterol from your diet.

Can Keto Cause Diabetes?
Keto doesn’t cause diabetes, with several studies proving that it can actually reverse, or lower it to the extent that results in less insulin dependence. Lower blood sugar levels will result in lower insulin levels, but it’s not a case that insulin can no longer be produced.

Is There Any Way of Avoiding these Symptoms?

There are several ways that you can avoid symptoms of all the negative side-effects you could experience when starting out with keto.

However, there isn’t a single pill or magic bullet that will make it plain sailing. It will take some experimenting, but we do want to give you a few options that will reduce the chances of feeling those dreaded “keto-flu” symptoms.

Keto Diet side effects

1. Drink More Water

You might be surprised that a loss of just 2% of water in your body is defined as dehydration. Because your new food intake will have significantly less volume (especially fruit and veg), you will be taking in less water through your food.

Within just a few days you can suffer from many of the symptoms discussed above, so make sure that you add 1 to 2 pints of water to your normal water intake.

2. Increase Your Sodium Intake

Salt is generally one of the enemies of a healthy diet, but without the right levels of sodium in your body, nerve and muscle functions can be severely impacted. Because your aim is to lower blood glucose levels, you will have lower insulin production.

While insulin is vital to the control of blood sugar levels, it also sends a message to kidneys to store sodium and water. With lower insulin, comes less water and sodium retention, which is why a little bit of unrefined salt on your food is a good idea.

3. Increase Mineral Intake

Because you will be removing most vegetables and fruit, you could see a sudden drop in minerals and vitamins. The minerals that are most commonly lost are sodium (see above) Potassium and Magnesium. (Find out more here)

One way to make up for the loss is to eat more salads that include avocado, spinach and lots of seeds. If you’re struggling to add enough, then simple mineral supplements will work perfectly fine.

4. Making Sure You're Eating Enough Fat

A faster way of achieving a state of ketosis is to increase your fat intake significantly. Medium Chain Triglycerides (MCT) are the best ones to source, as they are metabolized faster into energy.

Coconut oil is a great source, and adding some to your snacks, lunch, and dinner is a great way to keep your energy levels up.

5. Stick To Low-Intensity Exercise

One mistake many people make when they start out is that they stick to high-intensity exercises. In the first few days and weeks, your body will still be adapting, and you will be suffering from low energy levels.

Draining your body of even more energy will just amplify the keto-flu symptoms, so make sure you turn it down a bit at the gym.

6. Reduce Stress

One common thing many people experience is a feeling of stress and brain fog, where they cannot focus on simple tasks. As your body shifts away from producing glucose, it will interpret the lack of carbs as a sign of starvation.

This causes cortisol to be released, which is a hormone that directly impacts stress levels. Making sure you avoid stressful situations in the first couple of weeks is a good way to reduce these hormone levels. And some meditation works very well too.

7. Get Enough Sleep

Not getting enough sleep can amplify hormonal imbalances and the groggy feeling. When low energy levels are met with lack of sleep, you can start feeling even more drained. By aiming to get an extra hour or two of sleep each night, you can reduce that risk significantly.

It’s not something you need to do long term, just for the first few weeks.

These 7 tips are simple things that will go a long way to preventing and reducing side effects. If they do persist, then you might need to look at some other supplement options, and we’ll take a look at some in the next section.

Other Things That Help With Symptoms:

fish on a plate white green sidedish

When your body doesn't ingest carbohydrates, it creates ketones for energy, typically from stored fat. However, there are also ways to get them easily from external sources.

The three different types of ketones that your body runs on are: Acetoacetate, Beta-Hydroxybutyrate, and Acetone. Beta-hydroxybutyrate is the active form that can flow freely in the blood and can be used by your tissues, so that is the one that most of these products are mostly based off of.

When you're experiencing side effects from keto, it's usually from a lack of these precious compounds themselves. This is where ingestible ketones come into play.

1. BHB

While these crystals may not raise ketone levels to an absurd amount like esters, their taste is much more manageable, and the potential diarrhea side-effects are lessened to a significant degree.

For the majority of the population, this is the type of product they should be looking for.

This is where the chemical (again, typically beta-hydroxybutyrate) is bound to a crystal — sodium, calcium, or potassium.

BHB Product

This is the go-to product that can help with most of the keto side-effects listed above, especially dehydration, cravings, and flu symptoms.

2. Esters

Esters are the raw ketone (in this case, beta-hydroxybutyrate) that are not bound to any other compound.

This external compound can be utilized a little quicker and can potentially have a better effect at raising blood ketone levels as your body doesn’t have to cleave the BHB from any other compound. 

beta hydroxybutyrate sign

The downside to esters, however, is that they just might well be the worst tasting thing on the planet, which is why we recommend the above type first.

3. MCT Oil

MCT (medium chain triglyceride) oil and other medium-to-smaller chain fats can be used to help boost the compounds in your body as well.

However, this is through an indirect pathway. Whereas BHB from crystals or esters can be immediately used for energy, MCTs have to be shuttled to cells to be broken down, after which ketone bodies are made as a byproduct, and only then can they be used for energy.

MCT Powder

The downside is that they do little in raising the actual blood levels of ketones.

Also, MCT oil is quite calorically dense, meaning it’s not a great solution for those looking to burn fat and keep calories low.

But it does indeed help with muscle cramps, dehydration, appetite control and other keto diet side-effects.

Final Thoughts

If you do still struggle with keto diet side-effects, a last resort would be to slightly increase the amount of carbs you’re eating to alleviate symptoms.

The downside to this is that it will make your low-carb diet less effective, but sometimes that’s necessary so you can continue the diet over the long-term and improve your health.

Overall, do your best to continue following the correct guidelines while also listening to your body and you'll be burning fat in no time.  

When the going gets tough, use proper supplementation to reduce the temporary adverse effects of the lifestyle.  

If you want to know more about what keto products are out there and what the best ones are, check out our page here.