One of the most common complaints I hear from patients that are starting on a low-carb or ketogenic diet is “Hey Doc, why am I exhausted on the keto diet?”

There’s usually a few good reasons for this “keto fatigue” and a few simple fixes to regaining your energy while being able to continue on a ketogenic diet.

Keto fatigue cause #1 – Dehydration

One of the first issues I see with people starting a ketogenic diet and complaining of fatigue is that they haven’t increased their fluid intake for the first few weeks. As you start a low carb diet you’ll notice that you’ll be headed to the bathroom more frequently. Part of these frequent calls of nature is due to an increase in your blood ketone levels, which will cause the kidneys to produce more urine (diuresis).

Another reason for the increased urine production when starting a ketogenic diet is because of slightly lower glycogen storage in the body while your body is adapting to a low carb diet. Every gram of glycogen stored in the body is stored with four grams of water. As the glycogen is released into the blood as glucose, the water stored with the glycogen is also released. ((https://www.ncbi.nlm.nih.gov/books/NBK499830/))

Since you aren’t eating many carbohydrates, your body isn’t fully restoring its glycogen levels in the liver and muscles, so less water is needed. So be sure to remember to stay well hydrated while starting the keto diet and that should help prevent one cause of fatigue and exhaustion on the ketogenic diet.

Keto fatigue cause #2 – Not enough electrolytes

The “keto flu” is real for some people and this “flu” can make you feel exhausted on the keto diet. One cause of the “keto flu” is not enough electrolytes such as sodium, potassium and magnesium in your diet.

Because of the excess urination for the first week on the ketogenic diet, you can also lose more sodium and other electrolytes, and this drop can make you feel tired or cause the “brain fog” that some people starting the keto diet complain of. Be sure to focus on foods high in potassium (green leafy vegetables), magnesium (nuts like cashews and almonds), and adding a little extra salt to your food and see how that helps with your “keto fatigue.” Sipping on both broth can also help replace some of the lost electrolytes.

Your body will eventually balance out and you shouldn’t need to continue to add extra salt to your diet unless you exercise a lot and are a heavy and salty sweater.

Keto fatigue cause #3 – Not in ketosis

If you’re cutting your carbohydrate intake just slightly and not limiting carbohydrates to the recommended 30 to 50 grams a day, you may not be reaching nutritional ketosis AND your body is also lower on carbohydrate intake. The result of not dropping your carbohydrate intake low enough to induce ketosis may leave you feeling weak, tired and lethargy.

One tip is to monitor your blood ketones daily when you start the ketogenic diet. There are several blood ketone meters on the market that can quickly measure your blood ketones from a drop of blood from a fingerstick.

If you’re struggling with getting your blood ketone levels up, read our “11 Tips to Increase Ketones Quickly” article.

Keto fatigue cause #4 – Too much exercise

If you’re an avid runner, weightlifter, or just like to work out, you should probably dial back your exercise program for the first couple of weeks or else you’ll find yourself exhausted on the keto diet. It can take several weeks to begin to become fat-adapted and where you can take advantage of the increase in fat metabolism with exercise. For some people starting keto, this adaptation may even take several months, so you’ll have to see how you do. However, there are elite athletes who follow a keto-like diet called the Optimized Fat Metabolism diet. Zach Bitter, an ultra-runner recently set the 12-hour running records on a track and a treadmill following a low-carb diet.

Keto fatigue cause #5 – Not enough calories

You might not feel as hungry on the ketogenic diet and end up eating a lot fewer calories every day. While this drop in calorie intake can be great for your waistline and the bathroom scale, you may notice that you do feel more tired on the ketogenic diet. If the big drop in calories is the cause of your exhaustion on the keto diet, try adding a snack of macadamia nuts or almonds to give you some extra calories.

Keto Fatigue cause #6 – Not enough sleep

The first time I started the ketogenic diet, the first thing I noticed is that I was waking up very early every morning. Some mornings I would be awake at 4 am and get out of bed to start my day. While this early morning routine was great at the start, I noticed after a week or so that my body really did need its normal 7 hours of sleep. It took a little bit of work, but once I was able to resist the urge to get out of bed if I woke up early, I found that my energy didn’t wane in the evening.

You don’t have to feel exhausted on the keto diet. The main causes of this fatigue and tiredness are usually easily fixed, so hang in there!