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Physical Signs and Symptoms of Ketosis.
Today we’re discussing the signs of ketosis. More specifically, physical signs and symptoms that you would experience in your body when you’re ketosis, without needing to do blood test or checking your urine for ketone levels.
The low carb ketogenic diet has been a very successful way for many people to lose weight and body fat and stay healthy. It’s arguably the most successful and sustainable low-carb diet to date.
When you begin keto, your body will go through a lot of physiological adaptations as it starts using ketones as your source of metabolic fuel for your body and brain in a state called ketosis.
So being in ketosis is the initial goal for many keto dieters. Once your body is in that state, the magic then begins to happen. But how do you know you’re in ketosis?
There are different ways through which your body tells you that you’re in ketosis. The most accurate way of confirming is by measuring your blood ketone levels with something like the blood ketone meter.
However, the strips can get pretty expensive to be honest and no one really wants to prick their finger with one of these several times a day.
Another way of knowing if you’re in ketosis is measuring urine ketones via a “spot test” with a dipstick. This is a much cheaper alternative to the blood measurement. However, the results can be a little bit inaccurate and difficult to interpret sometimes.
In the vast majority of the cases we will hardly need these tests unless we’re in a clinical setting. And many people who have started keto would simply want to be able to use the signs and symptoms from their body to tell accurately if they are in ketosis or not.
So whether you’re just starting out on a ketogenic diet or you’ve been on one for a while, here are 9 positive and negative signs of ketosis you may experience bodily, that tells you that you’re in ketosis.
Physical Symptoms and Signs of Ketosis
#1. Keto Flu
Keto flu is so called because of the flu-like symptoms that you get. These symptoms may start showing up two or three days after starting a very low carb ketogenic diet. The signs of keto flu include feeling a bit of headache, a little bit fatigue or tiredness and maybe poor concentration.
To be honest I think calling it ‘flu’ is a little bit extreme wouldn’t you agree? If you’ve ever actually had the flu what you go through here is nothing in comparison. But it could well be the first time that your body is starting to burn fat as its primary fuel source.
You’re body is just not used to using fat as it’s source of metabolic fuel and it takes a little bit of a period of adaptation. So keto flu will be your first sign of being in ketosis.
#2: Bad Breath
Bad breath or keto breath is a symptom you’ll notice as the levels of ketones in your blood start to rise and you full ketosis. It’s a common side effect experienced when you’re on low carb diets like keto or Atkins.
It actually happens because one of the ketones escapes in the form of acetone and that is breathed out. Now not everybody can detect that some people can’t even smell that as your breath takes on a fruity smell.
In fact you may notice that your urine and sweat also smell bad for the same reason. This is what I personally experienced when I started keto.
How do you solve bad breath due to keto? Brush your teeth frequently as possible. Some people also chew sugar-free gum. If you decide to use gum to solve keto bad breath, always check the label to ensure that you’re not taking in extra carbs. This will raise blood sugar levels and reduce your ketone levels.
For the sweat you may use essential oils such as peppermint during your workouts. This will not only improve the smell but also your workout performance. Studies have shown that using peppermint can improve your performance output by up to 10 percent.
#3. Digestive Changes
It’s pretty common for people to have changes in their bowel habit after a few days of being on a low-carb diet. Your whole body is adapting to a new way of eating. And all your bacteria within your gut have also got to adapt to that way of eating.
And that means there’s going to be changes. Constipation and diarrhea are common side effects of keto. Now some people get constipated whilst other people get diarrhea. It’s usually pretty short-lived though and would go away.
How do you resolve these digestive issues? Supplement with fiber using acacia power or Psyllium husks. You should ensure you’re eating plenty of low carb veggies such as broccoli, celery or brussel sprouts.
#4. Decreased Exercise Performance
If you’re not really doing a lot of exercise you might not notice this one. However, if you’re a regular gym goer particularly if you’re doing weights, then you’ll probably notice that you won’t be able to lift quite as much as you normally do.
If you’re sprinting you might not be able to do that as quickly or go as far as you normally do. So the first reason for this is you’ve probably burned through your short-term energy stores.
When you go on a low-carbohydrate ketogenic diet the first thing your body uses up is your short-term energy stores which are glycogen. Glycogen is in the liver and your muscles.
It’s also glycogen that your muscles normally use for real short bursts of energy and that would be things like lifting heavy weights or sprinting. So those are the areas which you will probably notice the biggest difference in.
The second reason you might experience decreased exercise performance is because your body’s just not used to burning fat and ketones as its primary energy source yet. It takes a period of adaptation for your body to get used to those new fuels and that’s going to show up in your exercise performance.
But you need to hang in there as your body is making the switch. You will come back with improved performance afterwards.
Studies have shown that athletes who switch over to a ketogenic diet burned as much as 230% more fat when they exercised.
#5. Insomnia

When you’re on a ketogenic diet up to 70% of the energy your brain is supplied with can be from ketones. Now this is a very different energy source for your brain and it’s very common for people who aren’t used to being on a ketogenic diet to experience sleep disturbances or insomnia.
This usually goes away in quickly and is replaced by a better quality sleep than even what you knew of before you started the ketogenic diet.
These first five have been negative but usually pretty temporary symptoms of being on a low-carb ketogenic diet. They all happened during the early phases but but can be a sign that you’re on the right track if being in ketosis in the longer term is your goal.
You’ll be pleased to know that the next four are very positive and if you’re already on a ketogenic diet you’re probably going to have experienced some of these symptoms. You’re encouraged to leave a comment below and let me know if you have experienced these side effects.
Did they pass? How long did it take for them to pass and have you got any tips for other people who might be experiencing these symptoms? I’d love to hear from you.
These first 5 are the negative signs of ketosis if you will. Okay so let’s move into the final four which can be termed the positive signs of ketosis. Some people even refer to it as the benefits of ketosis or the keto diet.
#6. Reduced Appetite
So you’ve created the conditions in your body where you can now access your stored body fat as energy. As a consequence, you’re gonna be less hungry. You’re getting your energy from your fat stores.
This is great, it’s a really positive sign. It’s very often at this point that people decide hmm actually don’t need breakfast anymore and this is a really good segue into intermittent fasting. What’s more, the fact that you’ve got reduced hunger means that that transition to intermittent fasting can be much easier.
This is one of the reasons it’s often recommend people start a low carb diet before they actually start intermittent fasting. It sort of just naturally happens that way.
The second reason you’re probably not feeling as hungry is you’re not getting the huge insulin spikes after a carb-based meal that you would have been doing. And we know that that can drive hunger forward when you get reactive low blood glucose level.
#7. Improved mental clarity
The next positive sign of ketosis is improved mental clarity or focus. Now this is one of my favorites. I love the clearness of thinking and the mental clarity that I have when I’m in the state of ketosis. If you don’t experience this straight away, be patient. Once you’re body is fully fat-adapted, you will experience it.
It’s it’s just awesome and it’s well worth being on a ketogenic diet purely for that if it wasn’t for all the weight loss stuff. Ketones are a great source of fuel for the brain.
#8. Improved energy.
The next sign that you’re ketosis is improved physical energy levels. So you’re now accessing your fat is your primary store of energy. That’s giving you a much more even delivery of energy throughout the day.
So you often don’t get those afternoon carb crash slumps anymore. Hopefully your early phase insomnia would have cleared up, your sleep will probably be better at that point and you will be waking up more refreshed.
Often people need a little bit less sleep when they are on a ketogenic diet. These are great signs that you’re probably in ketosis.
#9. Losing Weight

Now I saved the best for last. The last of the signs of ketosis is the big one: you’re losing weight. If the reason you’re on a ketogenic diet is you’re trying to lose weight and you’re actually losing weight, then it’s really not worth bothering whether you’re actually in ketosis or not.
You’ve probably got enough evidence that you are in ketosis and you’re achieving your goal of weight loss. So losing weight for me is the biggest sign that you’re in ketosis.
You may be asking whether you’re going to be losing fat as well. The answer is yes, you will but you will lose weight first and as long as you stick to your keto diet, fat loss will happen.
Weighing on a regular basis you get to know fluctuations within your body weight that tell you whether you’re on the right track or not.
So now you know the nine signs that you’re in ketosis.
Conclusion
These are the signs of ketosis that will tell you that your body is starting to burn fat for fuel or it is actually do so. The initial negative signs of being in ketosis usually will go away in a couple of weeks or a few. However, the positive signs or benefits of keto are so great the initial negative signs pale in comparison.
The most accurate way of knowing that you’re in ketosis is through testing your ketone levels in your blood or urine.
But here’s the kicker. If weight loss is your primary goal of following the the keto diet, and you’re losing weight, there’s not need to be pricking yourself every couple of weeks checking for ketone levels.
Enjoy your weight loss, improved mental focus and clarity, better sleep and higher exercise performance. If you’re already on keto and experience any of the signs of ketosis that is not included here, share them in the comments below.