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The Keto Flu: Symptoms, Causes, and Remedies

person experiencing keto flu

The ketogenic diet depletes your stored glycogen and increases your ketone levels. While this diet results in fat loss, better blood sugar control, and many other health benefits, most people coming from a standard American diet who do keto initially experience keto flu.

Without understanding what the keto flu is, one can easily give up or assume that the diet is dangerous. This article helps to educate you about keto flu symptoms, why it happens, and what to do to ease them.

What is the Keto Flu?

The keto flu is a collection of symptoms that occur within the first few weeks of starting a keto diet. As the term implies, it feels like you’re having the actual flu although it’s not contagious – and neither is it dangerous.

Usually, symptoms start to appear on the third day and can be mild, moderate, or severe. They should be gone within a few weeks. Reports show that the keto flu peaks in the first week and diminishes in the fourth week(1).

Keto Flu Symptoms

Flu-like symptoms can differ for every individual, but the most common ones are the following(2)(3):

  • Headache
  • Fatigue
  • Nausea
  • Dizziness
  • Brain fog
  • Stomach discomfort
  • Diarrhea or constipation
  • Body aches
  • Cramps
  • Difficulty exercising
  • Irritability
  • Dehydration
  • Feeling sluggish

In case you’re wondering, yes, it’s possible for someone to have a fever during the keto flu. However, it should feel like regular flu – not with cough or shortness of breath. You should contact your healthcare provider if you feel the latter.

Keto Flu Causes

If you’re coming from a high-carbohydrate diet and drastically reduced your carbs, your body is going to react. It will try to adapt to its new fuel source, which is fat, during ketosis. Imagine your body screaming for carbohydrates and sugar. So, in addition to the symptoms mentioned above, you’ll most likely have extreme cravings.

Since your carb intake has dropped, your insulin levels drop too. This results in you urinating more frequently as your kidneys excrete electrolytes such as sodium and potassium.

That is why a properly formulated keto diet should include foods that are rich in these important electrolytes(4). Good sources include red meats, avocados, and leafy greens.

Important: If you’re planning to follow a keto diet and you have a heart or kidney problem, consult your doctor about your sodium and potassium intake.

Keto Flu Remedies

As mentioned earlier, these withdrawal-like symptoms do not last long. For most people, they appear on the third day and last up to 4 weeks. You will feel much better as your body adjusts its metabolism in which it burns fat instead of carbs for fuel.

Fortunately, there are steps you can take to help you get rid of the keto flu as soon as possible. Or at least make it less severe. Don’t panic, and most importantly, know that you’ll get through this.

1. Replenish your electrolytes

Protect yourself from losing too many electrolytes and combat their effects. A simple hack would be to drink water with a pinch or two of salt. You can also drink homemade bone broth as a delicious alternative, or try keto-friendly electrolyte supplements.

In addition, add extra salt to your home-cooked keto meals. Eat more electrolyte-rich keto foods like meats, fatty fish, leafy greens, nuts, and seeds. Of course, your choices depend on your intolerances, allergies, and personal food preferences.

2. Drink more water

Being dehydrated can make keto flu symptoms even worse. It increases headaches, cramps, and weakness. If you’re feeling thirsty, having a dry mouth, or observing dark yellow urine, increase your water intake.

Aside from drinking water, eat low-carb water-rich fruits and keto vegetables. Great options include cucumbers, watermelons, peaches, lettuce, and zucchini.

You can even make an electrolyte drink at home by mixing water, lemon juice, apple cider vinegar, sea salt, stevia, and ice. This would be a flavorful way to stay hydrated.

3. Eat more fat

Don’t be afraid of increasing your dietary fats on keto. A lot of newbies on keto make the mistake of decreasing carbs but not upping their fats. Keep in mind that when carbohydrates aren’t available for energy, your body has to get them from somewhere else. Aside from protein, it also needs healthy fats.

Fat helps your body produce hormones and absorb vitamins A, D, and E. It increases your satiety and energy. That way, you don’t go craving carbs and you’ll have the drive to complete your tasks.

Here are a few helpful ways to add fat to your diet:

  • Cook with butter.
  • Choose fattier cuts of meat such as pork ribs, ground pork, pork belly, lamb chops, ribeye steak, and chicken thighs.
  • Eat avocados if you’re on a plant-based keto diet.

4. Get quality sleep

The keto diet may improve your sleep long-term as one of its benefits. However, some people have difficulty sleeping while on the keto flu. This may be caused by muscle cramps, the body adjusting to its new macros, or feeling unwell in general.

If you’re dealing with insomnia, follow a relaxing bedtime routine. Take a warm bath. Turn off your electronic devices 30 minutes to 1 hour before bed. Do meditation with deep breathing(5).

5. Go easy on your physical activity

Starting a new diet can stress your body out, and the last thing you need is to feel worse than ever.

You can engage in light exercise such as walking or stretching. But do not exhaust yourself. Rest or take naps if you feel like doing so. If possible, have your spouse or family member help out with the chores.

Once your body adapts, you can resume your usual workouts.

6. Eat when you feel hungry

Do not worry about your calorie intake at this point. Save that for later, including other diet strategies such as fasting. Your focus right now should be on helping your body become fat-adapted.

Limit your carbohydrates to 50 grams or lower per day. Then nourish yourself with all the keto foods you can have. It’s normal to experience hunger often during the adaptation phase. Trust that you will feel much better soon.

When that happens, you’ll find that you’re not as hungry as you used to be. You may even reach a point in which you can go longer without food. Plus, you develop metabolic flexibility.

Make sure that you have access to keto-friendly snacks in case hunger strikes. The best ready-to-eat keto snacks include pork rinds, hard-boiled eggs, and beef jerky.

You can also try some of our snack recipes like keto cloud bread which is great for sandwiches. For a naturally sweet treat, try our keto strawberries and cream.

7. Try distraction techniques

If you’re serious about sticking to this diet, then find something to help you get through it. Using distraction as a coping mechanism helps a lot.

Engage in an activity you enjoy like watching a movie, talking to a friend, reading a book, or journaling. Just avoid anything that has to do with food. It might just increase your cravings.

How Long Does the Keto Flu Last?

The keto flu usually only lasts up to 4 weeks for most people. In some cases, it may last for more than a month. Keto flu symptoms become less severe as your body adapts to its new fuel source which is fat.

If you’re one of those who have a hard time adapting, you might want to slowly reduce your carbs. Implement the strategies we shared earlier to make the transition as easy as possible.

When to See a Doctor

The keto diet, when done correctly, should not lead to adverse side effects. That is why it’s so important to replace lost electrolytes, stay hydrated, and increase your fat intake. But if your symptoms worsen over time, it’s best to seek help from a doctor. You might have an undiagnosed medical condition.

The Bottom Line

The keto flu or carb flu is a normal part of the ketogenic diet. Anyone who’s coming from a high-carb diet will likely experience it because now they’re switching to a different kind of fuel.

Symptoms such as headaches, fatigue, and brain fog subside as you push through by following the strategies above. Remind yourself that these won’t last long. Soon enough, you’ll start to see that weight coming off, feel stronger, less hungry, and more focused. More importantly, your health improves.

If you liked this topic, please share it with your friends. Or share your thoughts/experiences in the comments below.

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Tiffany Joy Yamut, RN
Tiffany Joy Yamut, RN
Tiffany Joy Yamut is a registered nurse and author of hundreds of health and nutrition articles focused on the ketogenic diet. Her diagnosis of polycystic ovary syndrome (PCOS), along with being overweight and a family history of type 1 and type 2 diabetes, prompted her to find a diet strategy that would allow her to live as healthy as possible. She discovered the keto diet in 2019, which helped her lose 44 pounds and achieve healing. Tiffany directs most of her efforts to studying, applying, and writing about the keto diet to help others. She’s been featured in Perfect Keto, Ketogenic, Kiss My Keto, and other top health and wellness websites. Follow her on Twitter and LinkedIn.
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Evidence based

This article is based on scientific evidence, written and reviewed by experts.

The founders of Ketogenic Buddies are health care professionals. As we grow, we include other qualified subject matter experts as part of our content team.

This article contains scientific references. The numbers in the parentheses (1, 2, 3) are clickable links to peer-reviewed scientific papers.