Why Am I Exhausted On The Keto Diet?

Why Am I Exhausted On The Keto Diet?

Estimated time to read 8 minutes

The ketogenic diet is extremely popular, and it is only growing! In fact, in the U.S. alone, there was an 850% increase in the search volume of the term 'keto' between January 2016 and January 2020. The keto diet aims to attack your body fat by reducing your carb intake to around 20 to 50 grams a day, causing the body to gather its energy from fat instead! This puts the body into a state of ketosis and can cause rapid weight loss.

Due to the positive response of the keto diet as a tool for health benefits and weight loss, it can be difficult to find information for some of the more challenging aspects of keto. Keto fatigue can occur during the early stages of the ketogenic diet and though it does not affect everyone, it is a completely natural bodily response. In this blog, we explain why you may feel exhausted on the keto diet and what you can do to feel better.

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Why do I feel weak and tired on the keto diet?

You’ll probably be glad to hear that feeling fatigued whilst on the keto diet is not uncommon and there are ways to help tackle it! Whilst switching over from carbohydrates to fat, your body requires slightly more time to burn the fat for energy. This often makes people initially feel tired or weak, especially if you have had a particularly low carb week.

What Keto Does to Your Body

The Keto Diet teaches your body to use fat for energy, rather than carbohydrates. Naturally, this will make you initially feel a little strange as your body adjusts. Normally, your body will source energy from glucose, a simple sugar that is a large component of most carbohydrates. When you eat more carbohydrates than your body needs, this excess glucose is stored as fat, making you gain weight. 

The basis of the Keto Diet relies on not eating enough carbohydrates for this to occur. When this happens, your body is forced to find energy elsewhere, breaking down stored fat and turning it into ketones through a process called ketogenesis. Once your body begins this process, burning stored fats and producing ketones for energy, you will enter a metabolic state known as ketosis. This is where the diet gets its name! 

Essentially, the keto diet is a low-carb diet that forces your body into a state of ketosis. This means that your body will burn any excess fat you have stored up over time, as there is no excess glucose available anymore to store as fat!

Why do you feel so tired after being in ketosis?

As you can imagine, being in a state of ketosis presents a huge change that your body needs some time to adjust to. Your body has to quickly adapt to a different way of obtaining the energy it needs, causing temporary keto fatigue. The reason for this sudden tiredness is that your body is using up all of your stored glucose and not replacing it through carbs. This means you end up with low insulin levels in your bloodstream, causing you to lose a lot of bodily fluids. This can lead to mild dehydration, stress, and mineral depletion, which are all potential reasons you might be feeling so fatigued during this time.

Mild dehydration

Mild dehydration often occurs a few days into your keto diet journey, as your body's insulin levels start to drop. This drop causes your body to dispel more sodium and water into the urine and can make you experience mild dehydration.

Too Much Stress

As your body adjusts to the ketogenic diet, you may find that little things start causing you stress. This is due to the diet affecting your brain and nerve system, as it is feeding off of a different form of energy. Over time, this should naturally relieve itself and might even better your stress levels in the long run!

Mineral depletion

The ketogenic diet often lacks fruits and vegetables which hold key nutrients that are needed in our bodies for energy production. This lack of minerals can increase the chances of feeling exhausted on the keto diet.

Not eating enough

In the first few weeks of the keto diet, your increased fat intake may make you feel full and satisfied for longer periods than usual. As a result of this, you may be eating fewer calories than usual causing you to feel more tired.

Not Sleeping Enough

All of the above symptoms can lead to not sleeping well, and insomnia can cause weight gain. Your body is simply adjusting to a lack of sugar and once ketosis begins, your sleep will hopefully sort itself out!

Hormone Dysregulation

A change in diet can cause hormone changes in women. According to HealthLine, the keto diet may cause irregular menstrual cycles or amenorrhea after a period of time. This is due to a change in nutrients that will affect how your body functions.

When does keto flu start?

During any previous research into the keto diet, you have likely found something called the ‘Keto Flu’. Whilst this isn’t a literal ‘flu’ as such, it definitely feels like one. This can cause a range of symptoms such as dizziness, irritability, insomnia, fatigue, and poor focus, and usually happens about 2-3 days into your diet, as your body enters ketosis. Luckily, this usually doesn’t last too long and many people only experience symptoms for a few weeks. Some have even only experienced it for 24 hours!

What are the symptoms of Keto Flu?

The main systems of the keto flu include fatigue, slower brain function, headaches, and nausea. These side effects are extremely common during keto-adaptation and are mostly due to changes in your body's blood sugar levels.


As your body starts unconsciously craving sugar, you are likely to be more reactive and irritable. This is simply due to changes in your energy and glycogen levels.


Headaches are also due to sugar cravings, though they may also be caused by mild dehydration due to ketosis! 


Experiencing nausea on the keto diet may be scary, but it is natural as your body begins the adaptation phase. Your body and brain just need time to adjust, and your digestion system is getting used to different hormones.


Dizziness, like headaches, is often caused by mild dehydration due to an increase in urinating from a keto diet!

Brain fog

The low carb diet may also cause a brain fog sensation and you may find it hard to remain focused or concentrated for periods of time.

How Do You Ease or Cure Keto Flu?

Whilst experiencing the keto flu, you may feel like the keto diet isn't working. In fact, this is actually a sign that your body is successfully adjusting to this new low-carb diet! Despite this, this adjustment period can feel uncomfortable, and luckily, there are also some things that you can do to help you get over the bad patch.

Salt everything

Increasing your salt intake will help any mild hydration that you are experiencing. This will ease any headaches and dizziness. The added salt can also help to reduce stomach cramps and nausea as it will replace lost electrolytes.

Keep your fats and calories high

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Increasing your fat and calorie intake will help to reduce symptoms of the keto flu. Part of the keto diet is satisfying your hunger cravings, but this may actually lead you to consume fewer calories than your body requires. Make sure you plan your meals alongside your macros to reduce the chance of this happening.

Eat More Frequently

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Similar to the above point, eating more frequently can help to regulate your blood sugar levels, reducing sugar cravings that cause headaches and irritability from a keto diet.

Eat enough fat

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Not consuming enough fat is a common mistake that most people at the start of their keto journey will make! Eating enough healthy fats will help your body to reach ketosis faster, easing the symptoms of the keto flu.

Avoid Dirty Keto

Dirty keto is when people rely on fast food to reach their macros for their keto diet. Though this may be convenient for some, it can be unhealthy due to limited nutrients entering the body. Try introducing some low-calorie fruits into your diet. Alternatively, Proper Goodoffers premade keto meals that are full of essential vitamins!


Exercising is a great way to keep your mood and energy levels high! However, do remember to rest if you're still feeling slightly unwell. Instead, maybe opt for lighter exercisesuch as stretching or yoga.

Sleep well

Though the keto diet may make it difficult at first, try to always get around 8 hours of sleep a night. Your body has time to recharge and regenerate whilst you are asleep, and this will also make you less hungry the next day.

Drink More Water

Drinking more water will help to decrease the nasty side effect of mild dehydration, which can cause headaches, brain fog, and dizziness. Water can also be a great energy source, so it may also make you feel more invigorated without increasing your carb intake on your keto diet!

Is there a medication for keto flu?

Doctors will most likely not be able to prescribe you anything specific for keto flu, but we recommend taking some over-the-counter electrolyte supplements to ease any symptoms you are experiencing! Medical experts also suggest magnesium or fiber supplements for a keto diet too.

When to see a doctor?

If the keto flu symptoms last longer than 10 days, or if they’re debilitating or painful, seeing a doctor is recommended.


In summary, feeling tired during the initial phase of the keto diet is completely normal, as it's your body adjusting to its new method of burning fat! These symptoms of keto flu will often get better within a few days and taking electrolyte supplements will help speed up the recovery process. If you have been on the keto diet for a while and you are still experiencing fatigue, it may be a sign that you are not consuming enough fats or calories that your body requires for energy. It is important that you feel comfortable and healthy, so make sure you seek professional help if you feel that you need it.

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