The “keto flu” can be unnerving if you don’t understand it.
Without prior knowledge, the symptoms can lead a new keto dieter to believe the diet isn’t working for them. Thankfully, that’s not the case at all!
The keto flu is a natural reaction to entering ketosis, it’s very temporary, and there are ways to remedy it. We’ve included all the details you need to know about the keto flu and what to do if you experience it.
In this article, you’ll learn:
Your body burns carbohydrates (glucose) for energy by default.
But when your carb intake is drastically reduced, like on the ketogenic diet, your body is depleted of stored glucose and instead turns to burning fatty acids for energy. This is the metabolic process of ketosis.
The keto flu is a natural reaction to our bodies are entering ketosis and switching to a state of glucose-burning to fat-burning.
Your body’s response to entering ketosis can often mimic symptoms of the flu, thus the name “keto flu.”
Most people experience the keto flu when they first start keto. Here are some of the most frequently reported manifestations of it:
- Stomach aches or pains
- Brain fog
- Dizziness or confusion
- Diarrhea or constipation
- Muscle cramping or soreness
- Lack of concentration or focus
- Trouble falling or staying asleep
- Sugar cravings
- Heart palpitations
Keto flu symptoms usually occur within the first day or two of starting a ketogenic diet, and the severity and length of symptoms vary per person. Some people may have no symptoms at all, while others could experience several for up to a week or two.
Either way, the symptoms shouldn’t last more than a couple weeks and should go away once your body is adapted to burning fat for fuel.
The keto flu is essentially the result of three things:
- Becoming “keto-adapted.”
- Electrolyte loss and dehydration.
- Withdrawal from carbohydrates and sugary foods.
Our bodies have two primary sources of energy:
- Glycolysis: converting glucose into energy
- Beta-oxidation: converting fat into energy
Keto-adaptation means getting the body used to the process of beta-oxidation. This is easier for some bodies than others.
Metabolic flexibility refers to how well a person can adapt to using a different fuel source: switching from burning glucose to burning fats. Those with less metabolic flexibility are more likely to experience keto flu symptoms as the body adjusts[*].
Genetics also play a part. Some people are simply better able to handle the energy switch.
The standard American diet contains a lot of processed foods, which are high in added sugars and salts. When we switch to a keto diet of whole foods, most salt-laden choices are eliminated and sodium intake is drastically reduced.
Sodium causes the body to retain water, so less sodium intake means less water retention. The lack of carbs also lowers insulin levels. All of this leads the kidneys to release excess water[*].
With that excess release of water, electrolytes are flushed out, leading to electrolyte imbalance and dehydration. This can cause flu-like symptoms until everything becomes balanced again.
Some research has shown sugar affects the brain in a way similar to heroin or cocaine[*]. It’s pleasurable, and we get a nice shot of the “feel good” hormone, dopamine, when eating sugar.
Plus, the addictive nature of these foods doesn’t help[*].
When sugar is drastically reduced from starting a keto diet, we can experience withdrawal effects like mood swings, irritability, cravings for sugar, and other symptoms of the keto flu.
Someone who has come from eating a diet full of processed and refined carbs and sugars is more likely to also experience these withdrawal-like symptoms and have more trouble adapting to fat burning.
Now that we’ve covered the “whats” and “whys,” let’s talk about how to alleviate these issues.
Although the keto flu is temporary, there are things we can do to reduce or even eliminate symptoms during the transition into ketosis.
The water loss that occurs at the beginning of a ketogenic diet needs to be replenished. This can help reduce keto flu symptoms like headaches, fatigue, or nausea that are often caused by dehydration.
Keep water near you to drink regularly throughout the day. Always drink when you feel thirsty.
If your urine is yellow, you need to drink more water. Clear urine is an indication that you’re well hydrated.
Often thirst is a sign of dehydration already, so try to get ahead of it.
As mentioned above, electrolyte imbalances can cause keto flu symptoms. Here are some of the best ways to mitigated this:
- Increase your salt intake. This will help counteract the water loss that happens when starting a keto diet and replenish sodium.
- Drink bone broth. Bone broth is not only an anti-aging elixir, but it provides electrolytes like sodium and potassium while also being hydrating.
- If you don’t want to drink bone broth, supplement with magnesium and eat keto foods high in potassium like leafy green veggies, salmon, nuts, avocados, or mushrooms. See our Vitamin and Mineral Supplement guide for more.
Get Plenty of Sleep
Getting at least seven hours of sleep a night is important for anyone, and even more so for the keto dieter.
Your body is experiencing a lot of changes as it switches fuel sources, so getting plenty of sleep can help reduce stress and fatigue.
If you struggle to get enough sleep per night, try incorporating a power nap or two into your day.
Do Light Exercise
Exercise performance may temporarily suffer while the body is adapting to higher fat and low carb intake.
At the same time, getting light exercise 2-3 times per week can help make your body more efficient at switching between carbs and fats for energy[*], helping to decrease keto flu symptoms more quickly.
Increase Fats and Calories
Your body is no longer getting its energy from carbohydrates and sugars, so it needs plenty of fat for fuel. Make sure the calories from carbs are replaced by eating plenty of keto-friendly fats.
Supplement with MCT oil powder to help further increase ketone levels for fuel.
If the keto flu is persisting longer than a week, re-evaluate your macros. You might still be eating too many carbs and not enough healthy fats!
Take Exogenous Ketones
Exogenous ketones are ketone salts you can ingest.
They provide your body with additional ketones to help it become more fat-adapted and enter ketosis more quickly. This can be really helpful in preventing or even eliminating keto flu symptoms.
Be Patient and Take Care of Yourself
Use the healthy tips above to help reduce symptoms and possibly even avoid the keto flu all together. Also keep in mind that the keto flu induction phase is just the beginning, and if you experience it, symptoms will subside; just give them time.
Once the hard part is over, you’ll be reaping the benefits of keto and thanking yourself for staying strong.