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Ketosis Symptoms: 10 Signs and Symptoms You’re In Ketosis

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Not sure you’re in ketosis? Here are some of the ketosis symptoms to be on the lookout for when you’re starting a keto diet!

Ketosis is the goal of following the keto diet.

Ketosis is a metabolic process and occurs when your body adapts from burning carbohydrates (glucose) as its primary source of fuel to burning fat, instead.

When your carbohydrate consumption goes low enough (<50 grams per day), your liver then converts adipose tissue and dietary fats into a fatty acid that is known as ketones and then burns the ketones for energy.

Achieving and maintaining a state of ketosis is very individualized. For some people it can take 3-5 days, for others it can take up to 2 weeks!

Achieving ketosis isn’t easy. And it is common for people to think that they are in ketosis when they actually aren’t. This could be because their carbs are low, but not low enough. Or that they’ve had a ‘cheat day’, which brings them out of ketosis.

Your body will not enter ketosis as long as there are enough carbs to use for energy. This is why there isn’t such a thing as a “cheat day” on the keto diet because increasing your carbs will take you out of ketosis. Which ends up defeating the point of following the keto diet in the first place.

But how do you know you have actually entered this state of ketosis?

Signs You Are In Ketosis

Ketosis causes a variety of changes in your body – some temporary, and some long-lasting (as long as you maintain your state of ketosis). These changes can be used as cues or “signs” that your body is in ketosis.

Some of these symptoms are rather unpleasant (tiredness, bad breath, headaches, etc) – but luckily the unpleasant symptoms are short-lived.

Ketosis Breath

While this may not be good for your social life, it’s a positive sign for your diet.

When you get into ketosis, you will notice your breath having a bit of a ‘fruity’ smell. It is a very common side effect for people on the keto diet, and other similar low-carb diets like Atkins (though not everyone experiences this side effect).

The smell is caused by elevated ketone levels. Specifically, the ketone called acetone. As you’re adapting to keto, your body produces more acetone than usual. Acetone leaves the body in your urine and breath, hence the smell. (And if the name sounds familiar – acetone is the main ingredient in nail polish remover!)

You can’t avoid it, but you can cover the smell by brushing your teeth more regularly or using gum.

If you do use sugar-free gum, check the ingredients, as some sugar alternatives still affect your blood sugar.

The good news is that this isn’t permanent – ketosis breath normally disappears after being in ketosis for a few weeks.

Weight Loss

I’m guessing you started the keto diet with the aim of losing some weight?

One major symptom of being in ketosis is losing a significant amount of weight in the first couple weeks of going keto.

Before you get too excited – this is mostly water weight.

But where does that water come from?

When your body stores glucose (sugar), it does so in the form of glycogen. Glycogen is made up of 3 water for every part glucose.

When you first get into ketosis, your body burns through all its glucose stores (because it is used to burning glucose for energy).

But the weight loss doesn’t stop there. Once your body has burned through all the glucose, it switches to burning fat. And that is when the fat loss happens.

Loss of Appetite

Many people find that overall, their appetite is less than before.

It is not yet understood why this occurs. It has been suggested that it may be due to alterations to your body’s hunger hormones, the increased protein and vegetable intake, or ketones possibly affecting the brain to reduce appetite.

Research is still being conducted. But in the meantime – make sure you are eating enough by filling up on healthy fats and fibrous veggies.


Of all the symptoms of ketosis – this is the one I struggle with the most. I need my sleep! I try to get into ketosis as quickly as possible, so I can hopefully avoid sleepless nights.

Interestingly – the insomnia is usually caused by carb withdrawal. It can happen in two ways.

Firstly – because sugar is physiologically addictive, when you cut it out you experience withdrawal symptoms. Insomnia is one of the symptoms of withdrawal.

Secondly – your body is in the process of switching from burning glucose for fuel, to burning fat for fuel. When your body doesn’t have any more carbs to burn, but isn’t yet used to burning fat, your brain can release cortisol at around 2-4am. This cortisol tells your body to wake up and get food.

If you find yourself experiencing insomnia, you can try to take melatonin for a couple of weeks until it subsides. Melatonin is a natural sleep supplement that is safe, but effective.

Once you have become fat-adapted, you may find that you actually sleep better than you did before following the keto diet.

Digestion Problems

This symptom is a good one to be prepared for beforehand.

Any major change in diet is going to affect your gut negatively for a while. Your gut has been used to processing certain types of food for so long, and now it suddenly has to deal with all new kinds of foods.

It’s going to be a little confused for a bit. You may have to deal with cramps, constipation, diarrhea, or a combination of these.

If you’re feeling constipated – make sure you are eating enough fiber-rich vegetables such as broccoli, kale, and asparagus.

Dehydration can also cause digestive issues, so make sure you are well hydrated (not just with water, make sure you are also getting enough electrolytes).

Eating a diet that lacks diversity may also be a cause for digestive issues. Be sure to include a variety of meats, vegetables, and healthy fats in your diet.

And lastly – if you have added anything new to your diet, be aware that your body may have a certain sensitivity to one or more of these foods. If you still have digestive issues after a couple of weeks – this may be the culprit.

A good digestive enzyme will help here.

Increased Thirst

As a side effect of the water loss, you’ll experience, you may experience increased thirst and a dry mouth.

Not only this, but the increased ketones can also lead to dehydration and electrolyte imbalance.

It is very important that when you start following the keto diet, that you increase your water intake and take electrolyte supplements. Especially if you are an athlete.

Increased Energy

And not just increased energy – more steady energy levels too.

When you’re in ketosis, your blood sugar stays low and is stable – you don’t get the sugar highs and crashes that you do when your diet includes sugar and carbs.

Due to this, you will find that your energy levels stay very constant throughout the day (no more mid-afternoon slumps!)

You will also find that you have more energy than before. This is because ketones are a very efficient source of energy. Your mitochondria produce more energy with fewer free radicals when burning ketones.

This is a side effect that carries on as long as you are in ketosis.

Short-term Fatigue

Before you get to the state of increased energy mentioned above, you will most likely go through a period of feeling fatigued and possibly weak.

This is normal, and a result of your body being forced to switch from running on carbs to running on fat for fuel. It is one of the symptoms of what is known as “keto flu”, and will last for anywhere from a few days to a couple of weeks.

To help reduce fatigue, take electrolyte supplements.

Your body loses electrolytes during the switch because of the rapid loss of water (explained above in “Weight Loss”), as well as from the elimination of processed foods, which normally contain a lot of salt.

Try to avoid strenuous activity during this time, and keep to low-impact workouts.

Muscle Cramps

You’ll notice that many of the unpleasant side effects of entering ketosis are short-term, and can be eased by taking electrolytes.

Muscle cramps is one of those. As I mentioned, when you lower your carbs drastically, you lose a lot of water weight, which means you also lose a lot of potassium, sodium, and magnesium.

These minerals prevent cramping, so if you are suddenly experiencing cramps after starting the keto diet, you are likely in ketosis.

Supplement with electrolytes, but also make sure you are eating plenty of foods rich in these minerals, such as nuts, seeds, avocado, leafy greens, and fatty fish.

High Ketone Levels

Increased ketone levels in your breath, blood, and urine are a sign that you are in ketosis. This is not something you will be able to ‘see’ though, you will need to test it.

It is the most definitive way of knowing whether you are in ketosis or not.

I discuss different ways of testing your ketone levels, below.

Can You Avoid The Ketosis Symptoms?

It is understandable that you’d want to avoid some of the more unpleasant symptoms of ketosis.

While you may be unable to avoid them entirely, it is possible to reduce their effect, until your body becomes fat adapted.

This can be done by being committed and staying consistent. You need to commit to keeping your carbs between 20 and 30 grams per day. And you need to be consistent and keep your carb levels that low every day. Each time your carbs go too high, you get out of ketosis and have to start over again.

If you go only slightly higher, the side effects won’t be as extreme. But I find it just easier to keep within the 20-30 gram range, and rather enjoy all the benefits of being in ketosis.

Not sure how to start a keto diet? Check out this post on starting a keto diet and learn how you can get started today!

How To Measure Ketone Levels

These signs and symptoms we’ve spoken about are all subjective ways to tell if you’ve reached ketosis or not – except for the last symptom – elevated ketone levels.

If you want to know for certain if you are in ketosis, the best way is to actually measure your ketones.

The key to the keto diet – that a lot of people actually miss – is being in ketosis. With other low-carb diets, you just need to reduce your carbs to the recommended amount. But unless you are actually in ketosis, you are not following the keto diet correctly.

To accurately tell whether you are in ketosis or not, you need to measure your ketone levels. There are three ways you can do this – breath testing, urine testing, and blood testing.

Breath Testing

Remember how I said that acetone was the cause of fruity breath when in ketosis?

This is the ketone that is tested when doing breath testing.

Acetone is not directly responsible for your metabolism and is more of an indirect measure of ketosis, but acetone has been found to correlate closely to the levels of BHB in your blood.

Acetone is measured using a breath meter.

Breath meters are an affordable way to test your ketone levels, as they are reusable (unlike urine or breath strips).

Unfortunately, they are not very consistent in their readings.

Urine Testing

Urine strips test the “excess ketones” that are being excreted in your urine. Specifically, it measures “acetoacetate”, one of the three ketone bodies.

The testing can be useful as you are getting into ketosis but isn’t very reliable once you become fat adapted. This is because once you are fat adapted, your body gets better and more efficient at using up the acetoacetate.

The strips will then show a lower level of ketones, but in actual fact, you are in a deeper state of ketosis. You don’t necessarily have fewer ketones, just less spilling over into your urine.

Additionally, your level of hydration, as well as electrolyte levels, can affect the readings.

Urine testing is quick and cheap, but it is not ideal – especially as you get deeper into ketosis – as it is isn’t always accurate. (Plus – peeing on a stick can sometimes get a little messy.)

Blood Testing

If you’re looking for the most accurate way to test your ketone levels at home, then a blood meter is the way to go.

Blood meters test your levels of beta-hydroxybutyrate (BHB). BHB is found in the blood and is circulated and carried to your cells to be used.

Testing your levels of ketones by using a blood meter is done the same way that diabetics test their blood glucose. You prick your finger and squeeze a drop of blood onto a test strip, and then place the strip into the blood meter which reads the levels of BHB in your blood.

How To Get Into Ketosis

So we’ve spoken about the common symptoms that you’ll experience once you’re in ketosis. But how to do actually get into ketosis?

The short answer is – restrict your carbohydrates.

When your dietary carbohydrates are significantly reduced (to <50 grams per day) your body’s production of ketones increases to maintain a blood level at or above 0.5 mM.

Once your body achieves blood levels in the nutritional ketosis range (0.5-3.0 mM), it then begins a process called ‘keto-adaptation’.

If you want to try to avoid the unpleasant side effects – read my post on how to get into ketosis in 24 hours, but beware, it takes a lot of work.

Why Does Being Ketosis Matter?

As long as you’re losing weight, you may wonder why you even need to worry about being ketosis?

There are many health benefits of being in ketosis, in addition to simply losing weight.

Reduce Inflammation: This allows for more energy production, better healing, and overall better functioning of your body.

Mental Clarity: Your mental performance will improve, and you may even experience reduced anxiety and depression.

Mitochondrial Biogenesis: As your body switches to burning fat for fuel, the old, weak mitochondria die off and new, stronger mitochondria grow. This can also lead to more energy production.

Reduced Risk of Chronic Disease: A large number of modern diseases are rooted in chronic inflammation and mitochondrial dysfunction (for example cancer, depression, diabetes, heart disease)/ The combination of the reduced inflammation, and improved mitochondrial function allows your body to heal and mitigate disease processes more effectively. 

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