Spotting Ketosis Symptoms: 11 Telltale Signs You’re in Ketosis

Ketosis lies at the heart of the ketogenic diet (it’s in the name!) so understanding what it is, and knowing whether you’re in a state of ketosis is a key part of your keto education! It’s time to learn some ketosis symptoms!

Many people on the diet actually fail to reach a proper state of ketosis, and experience the benefits it can bring. Instead many people find themselves experiencing many of the negative side effects associated with the first few days of a keto diet, with these lasting for much longer than what is often described.

This is a telltale sign of someone being halfway into ketosis, with their body struggling to fuel itself efficiently.

Thankfully there’s plenty you can do to get into an optimal state of ketosis, and with these signs and symptoms below you’ll have a pretty good idea whether you’re on the right track.

It depends on your own body chemistry but if you’re just starting out on the keto diet it can take from a couple of days through to a couple of weeks for your body to really adapt to the diet, there are some significant biological changes inside happening to turn yourself into a fat burning machine!

What is Ketosis?

Ketosis is the way in which your body is going to be getting its energy when you’re eating a proper ketogenic diet. This is a process where you body breaks down fat cells in your fatty tissue, and the foods you eat, and converts the fats into energy to power your body and brain.

Ketones are the product of this process which lend their name to the ketogenic diet. These are converted to energy in cells and it is some of the by-products and side effects of this process that we will be looking for to know when we’re in a state of ketosis.

For your body to enter ketosis and use fats for fuel you have to deprive it of it’s favorite fuel source, carbohydrates! So long as there are carbs and sugars in your blood stream for your body to use it will do it’s best to use these, which makes it really easy to kick yourself out of ketosis with even a small carb heavy snack.

You will generally enter ketosis by heavily restricting carbohydrates, and increasing your fat intake to around 80% of your daily calories.

Alternatively many people enter ketosis through fasting, which leads to the same mechanism once you’ve burnt through all the sugars in your body. Only in this case you’ll be relying on the stored fats in your body for energy, which can be hard going in the first few days compared to eating additional fat through your diet.

The Ketosis Symptoms

This isn’t going to be an exhaustive list, but these are all the signs I tend to go through if I’ve fallen off the keto wagon and am trying to get back in,  and are common for just about anyone starting out on the keto diet.

These are all commonly reported ketosis symptoms and signs; some lucky people seem to be able to breeze through the early days of keto adaptation without any negative side effects, whilst others get the whole lot.

Whilst these symptoms don’t guarantee that you’re in ketosis, they’re usually a good indicator. If you find you have more than a couple of these ketosis signs then there’s a pretty good chance you’re into ketosis and should hopefully be starting to feel some of the benefits shortly.

Of course if you really want to be sure you can always test your body chemistry directly. Skip down to number 11 if you want to get scientific!

I’ve tried to list these out in the approximate order that I tend to experience them/measure them. I personally find that thirst is the first clue that I’m entering ketosis, with a dry mouth kicking in about 12-18 hours after my last carb based meal.

Many of these symptoms come about in those first few days of going onto a keto diet, as your body chemistry adjusts to it’s new fuel source. Most of the negative signs on this list should start to subside as your body becomes more adapted.

1. Thirst

ketosis symptoms - thirst

One of the first things to happen when you being entering ketosis is that your body begins to use up whatever glucose you have left in your muscles for fuel, releasing a lot of water in the process.

Unfortunately all that water also comes with a loss of electrolytes leading to electrolyte imbalance. What this means is that your body is actively flushing out water which can lead to major dry mouth and thirst!

This is my telltale ketosis symptom, as I’m usually pretty good at staying hydrated, drinking 2 – 3 litres of water per day.

What should I do?

Be sure to stay well hydrated, and try to add extra electrolytes where possible. Dehydration and electrolyte imbalance are one of the key causes of the dreaded keto flu so add some Himalayan pink salt to redress the balance, or supplement with a little potassium, calcium and magnesium to replenish these vital minerals.

If your thirst is very severe you may be cutting your carbs a little too much, too fast. Aim for around 30g of carbohydrate during the first days of your transition to a keto diet to avoid the worst of the ketosis symptoms.

2. Bad Breath

ketosis symptoms - bad breath

This is one of the first outwardly recogniseable ketosis symptoms to appear, if someone stops you to offer you some gum, you must be doing something right (keto wise at least…)

When you enter ketosis your body begins to break down fats into 3 main components and by-products:

  • Beta-hydroxybutyrate (BHB)
  • Acetoacetate
  • Acetone

These compounds are processed as part of ketosis to generate energy, with acetone being a by-product of the other two elements.

Your body excretes acetone a couple of ways, the first being through the lungs and your breath (you’re literally breathing your fat away!) and through your urine (…)

The acetone in your breath is the main cause for this bad breath, combined potentially with a dry mouth from thirst. This isn’t a sign of poor dental hygiene however, and will tend to get better as time goes on.

What should I do?

Stay well hydrated, as with the first keto symptom, and then deal with bad breath as you would from any other cause. Sugar free chewing gum, mouthwash and regular brushing should all help to mask the keto breath!

3. Increased Urination

ketosis symptoms - increased urination

All that water that’s being released from dropping insulin and glucose metabolism – gotta go somewhere!

Your kidneys are working overtime the first few days of ketosis to get rid of this extra water, as well as excess blood ketones in the early days.

This keto symptom should stop after a few days, up to a week whilst your body is readjusting.

You’ll lose a lot of weight the first few days on a keto diet, but in all honesty, this is going to be almost all water weight until your body adapts to using ketones for fuel effeciently.

I personally love the first couple of days transitioning back and seeing weight drop off, but you have to remember that that water weight can come back just as fast (which is why I don’t recommend weighing yourself too regularly, or in different scenarios – I’m 190lb but can fluctuate up to 6-7 lb over the course of a weekend!)

4. Fatigue (initially)

ketosis symptoms - fatigue and tiredness

This is one of the most challenging short term ketosis symptoms of a transition into ketosis, and is a common reason for people dropping out.

Your body is adapting to use fats for fuel, this is a biological shift throughout the cells in your body, and it takes time.

If this is your first time eating a low carb diet, your body is going to suck at using fat for the first few days/weeks.

What this means is whilst you’ve taken away the nice and easy carbs, your body isn’t able to make up the difference with all that lovely fat you’re giving it until it’s made the transition.

You’ve run out of energy!

You may have some mental fog, and at the very beginning some strong cravings for sugary drinks etc, but know that this subsides very quickly.

Now don’t go crazy, if you’re literally about to pass out, then get some carbs in you, some people can really struggle with low blood sugar. If so you may need to take your time to transition.

On the plus side, once this particularly part of the process is over your body will begin using fats for a fuel in a way it never has before – and with it come some of the best benefits of a keto diet like mental clarity and sustained energy levels.

What Should I Do

The key thing here, as with most of these ketosis symptoms is to stay hydrates, keep your electrolytes up, and don;t over exert yourself. The transition into a keto diet is not the time to take up sprint triathlon!

5. Weight Loss

ketosis symptoms - weight loss

As mentioned, the first week on a keto diet, you’re almost definitely going to lose some weight (if you’re doing it right!)

The reality is that for the first week or so that’s almost all water, with maybe a little fat coming off towards the end of the week.

It can be exciting seeing weight drop off fast but remember how easily that water weight can come back on, you need to keep going past that initial stage to see real fat loss.

Once this initial drop in weight is over though, a slower more sustained loss in fat should occur if you eat a slight calorie deficit. Your body will become better and better at burning fat for fuel as the weeks go on, though it can take some time to be fully fat adapted.



6. Toilet Trouble

ketosis symptoms - toilet issues

Now we’re getting onto the good stuff!…

Nothing too scary, but this is one of the common ketosis symptoms in those early days so best to be prepared.

Most people go one of two ways, either nothing comes out, or everything comes out, and then there are the lucky one’s who just carry on as if nothing ever happened…


With some dehydration, and a shift away from carbs (which are often our main source of fibre) – you may find yourself going for a few days at the start without going number 2.

The fix? Stay hydrated (again) and try to get some fibre into what you’re eating. I go for avocado, nuts, seeds (especially chia seeds, which i sprinkle liberally over smoothies).

Try to eat lots of green veggies with every meal too. This is something many people forget, a healthy keto diet should contain a lot of gree veg, don’t focus too much on just the fats.


Yep, this might happen. All that water your body is trying to flush out? Gotta go somewhere, and sometimes it just needs to get out now. Again, try to get more fibre in, stay hydrated and give it a couple of days to subside as your body’s water retention adjusts to a keto diet.

7. Decreased Performance

ketosis symptoms - decreased performance

This comes off the back of fatigue and the other symptoms listed above, and is a ketosis symptom you’ll most likely notice if you’ve been working out and are trying to transition into a keto diet.

You’re probably not going to do your best workouts those first days on a keto diet. In fact, to be fully fat adapted for the purposes of exercise, and reap some of the rewards this can bring, can take months!

This should subside as you adapt. for more information on working out on a keto diet you should give this keto exercise guide a read.

8. Insomnia

ketosis symptoms - insomnia

Lack of sleep. This, combined with fatigue can be a difficult combo, especially if you’re working or have a lot going on during your transition into ketosis.

This is caused due to an increase in stress hormones in the body during those first few days of carb restriction, before ketone levels replace the energy sought from carbs.

This should subside relatively quickly, and for many long-term keto adapted dieters their sleep is improved on a keto diet in the long term.

9. Reduced Appetite and Hunger

ketosis symptoms - reduced appetite

Up until now, we’ve been focusing on what are really some of the negative ketosis symptoms, and most of these are common and occur during the transition into ketosis. But the next is, to me at least one of the more enjoyable signs of ketosis.

Until you get into an optimal level of ketosis you’re not going to be feeling the full benefits of this way of eating, but once you get there, reduced hunger and cravings is one of the sure signs you’ve made it.

Your body carries tens, if not hundreds of thousands of calories of energy in the form of fat, and once you’re fat adapted and fully in ketosis you can access these fat stores easily for fuel.

With access to these fats, your caloric needs from foods may reduce as you tap into reserves.

Along with much more satiating fats and proteins being your main foods, this can mean going for much longer without noticeable hunger.

I personally find myself eating smaller portions once I’m in ketosis, and when I record my calorie intake I’m rarely hungry whilst eating a significant caloric defecit.

If you’re considering combining intermittent fasting with a keto diet (which I highly recommend for fat loss) then I would wait until you get to this point with the diet, before adding in the fasting.

Going for 16+ hours without food is just a lot easier once your body is better able to quickly get into ketosis. Otherwise you may be setting yourself up for a fall by trying too much, too early.

I love this sign of ketosis – I’ve found this has reset my relationship with food. I’m no longer a slave to cravings and out of control portion sizes!

10.Increased Energy

ketosis symptoms - increased energy

Finally onto the good stuff!

Once you’ve transitioned into full ketosis you may find yourself with endless energy. The fatigue from the transition stage falls away and you’re now able to focus for hours on end without getting drained.

Fats and ketones are a very efficient fuel source compared to carbs, and don’t subject you to the highs and lows that many have when eating sugar (I used to crash about 3pm every day at work after lunch!).

Having high, steady energy levels on ketosis is for me, one of it’s greatest benefits alongside weight loss, and the reason many non-overweight people try the diet.

11. Increased Ketone Levels

The last of the ketosis symptoms is for those who want to get scientific, want to know they’re in ketosis. If you’re keen on trying to reach an optimal state of ketosis then these 6 steps for optimal ketosis would be a good read.

If you’ve read this list and are experiencing a couple of the things up here, then you’re probably into ketosis to some extent. You may want to know for sure though, in which case you’ve got three options:

  • Urine Ketone Strips
  • Breath Ketone Analysers
  • Blood Ketone Readers

These go in order of accuracy and generally, cost. Lets look at each:

Urine Test Sticks:

These are what most people get at first to check whether or not they’re in ketosis at all. Whilst they’re not particularly accurate, and aren’t going to give you a clearly measureable number, they will let you know roughly whether you’ve made it into ketosis.

The method is pretty straight forward…pee on a stick. The stick will react with ketones excreted in the urine and change colour depending on the concentration.

I like urine strips as a starting investment in knowing how I’m doing. These strips are a good start to get the job done.

Breath Ketone Analysers

Remember that bad breath was one of the ketosis symptoms?

Well those were ketones you were breathing out from your lungs, and they can give a good indication of an approximate ketone concentration in your body, although not as accurate as blood testing.

Unlike the other two methods you won’t need to buy replacement strips for testing, which reduces the long term cost.

And for the squeemish amongst you, you won’t need to be dealing with any blood or sharp points…

A device like this Ketonix Breath Analyzer is a good starting point for breath testing your ketone levels.

Blood Ketone Testers

This is for the more hardcore amongst you who want to know for sure how far you are into ketosis. These testers are a much more accurate representation of your bodies chemistry, although you do need to break the skin for this one.

You’ll also need to get replacement strips for this which increases the long term cost, but if you’re keen to give it a try, the Keto Mojo is one of the most popular testers on the market.

We’re All Different

How many of the signs and ketosis symptoms have you experienced?

The reality is, ketosis can be different for everyone, some many experience all the ketosis symptoms whilst other may not at all.

It’s best not to compare too much with others, in the first couple of weeks especially, as your own body chemistry is going to be very different and may take longer to transition into full ketosis.

Once you’re there though the benefits, in my opinion, are worth the hassle of getting there. Let me know what you think and whether you’ve experienced any other signs of ketosis you think would be good on this list.

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Where to next on your keto journey?

1. Learn more about working out on the keto diet with our keto exercise guide

2. Learn more about the keto diet with our beginners guide to keto

3. Discover the signs and symptoms to know for sure when you’re properly in ketosis

4. Check out these tips and tricks to save money and lose weight with our keto on a budget guide

5. Stock up your keto cupboard with this list of ready to eat keto snacks

6. Keto in a hurry? Make one of these keto friendly smoothies to fuel your day

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