‘Keto Flu’: What It Is and How To Manage It

The ketogenic diet is a therapeutic diet that can do a lot of good for people with diabetes, epilepsy and other conditions. But when you’re just starting out, a group of symptoms referred to as “keto flu” can make you feel pretty bad for a little while.

It’s important to understand that keto flu isn’t the real flu — or an actual illness at all. But it can still make you feel really crummy, which is how it got its name.

So, what exactly is keto flu, and how long does it last? Registered dietitian Beth Czerwony, RD, LD, weighs in.

What is ‘keto flu’?

The goal of the keto diet is to reach ketosis, a metabolic state where your body burns fat for energy instead of glucose. But when you first reach ketosis, you can experience some pretty unpleasant symptoms known as keto flu (also known as keto induction or keto adaptation).

“Keto flu is a group of symptoms that can appear anywhere from two to seven days after someone is in ketosis,” Czerwony explains. “They’re a sign that your body is adapting to the new diet.”

But not everyone who follows the keto diet experiences keto flu. And unfortunately, there’s really no telling whether it will affect you.

“There’s no explanation of why some people have these symptoms while others don’t,” she continues. “And you won’t necessarily be more successful at weight loss if you have (or don't have) these symptoms.”

Symptoms

Image content: This image is available to view online.

View image online (https://assets.clevelandclinic.org/transform/4e6e2495-90d3-45af-9bc1-27a0fe9a03f8/keto-flu-infographic)

Symptoms of so-called keto flu may include:

• Brain fog
• Constipation or diarrhea
• Fatigue
• Feeling “hangry”
• Headache
• Irritability
• Muscle cramps
• Nausea
• Trouble falling asleep
• Upset stomach

How long does it last?

Good news: Keto flu won’t last forever. Symptoms last for as little as two days or as long as a month, but usually somewhere in between.

“Symptoms typically occur for one to two weeks,” Czerwony says, “but they eventually lessen and resolve on their own.”

Some people report that when symptoms clear up, they feel like the clouds have parted and the fog has lifted — like they’re clearer-headed than ever.

But what should you do in the meantime? Let’s take a look.

How to manage keto flu

While there’s no surefire way to prevent keto flu, there are ways you can take care of yourself while you’re going through it. Here’s what to try.

Drink water

“Eliminating carbohydrates from your diet can lead to dehydration,” Czerwony reports. “To stay hydrated, drink plenty of plain water or sugar-free electrolyte options.”

There are a few reasons for that dehydration, all of them very scientific — but the bottom line is that upping your water intake can go a long way for your body, especially if you’re starting the keto diet.

Replace your electrolytes

The keto diet restricts certain foods. But those foods provide you with important electrolytes, like:

• Sodium, which helps your cells maintain the right balance of fluid
• Potassium, which counterbalances sodium and helps your muscles contract
• Magnesium, which helps your cells as they turn nutrients into energy

To make sure you’re getting enough, make a conscious effort to replace them with keto-friendly foods, such as:

• Avocados
• Bone broth
• Leafy greens
• Nuts
• Salmon

Using a little bit of salt in or on your meals (as needed) can also help replace lost sodium.

Eat more often

During the keto flu phase, you may feel hungrier than usual and even experience significant food cravings, like for sugary foods and simple carbs.

“Eating more often and focusing on a good variety of foods (within what’s allowed on the keto diet) can help with hunger and can also decrease nausea,” Czerwony says.

It’s also important to make sure you’re eating enough fat and protein. If you’re lacking in either, you may not feel full — and the hunger pangs will continue.

Prioritize rest

When you have a virus or a cold, you know that rest is key. And when you’re dealing with keto flu, the same is true.

“Your body is adjusting to some major dietary changes,” Czerwony says. “So, while you’re experiencing keto flu, it’s best to give yourself a break.”

Avoid vigorous physical activity and embrace good sleep hygiene practices until symptoms like fatigue, muscle cramps and irritability pass.

Try a different diet

Keto isn’t for everyone. Just because it worked for your mom or friend or that lady you talked to in the checkout line of the grocery store doesn’t mean it will be the right fit for you.

“Some people find that it’s best for them to transition away from keto and into another low-carb diet instead,” Czerwony notes. “But this type of transition is best done slowly and with the help of your primary care provider or a registered dietitian.”

Can you avoid it?

For some people, introducing the keto diet slowly helps keep keto flu at bay. So, if you’re reading this before you’ve started your keto journey, consider gradually reducing carbs from your diet, rather than eliminating them all at once.

But here’s the biggest tip of all: Don’t start the ketogenic diet on your own.

“Any time someone decides to eliminate any food group from their diet, they should run it past their primary care provider first,” Czerwony stresses. “Some medications, like those for blood pressure and diabetes, can actually make symptoms worse.”

A registered dietitian can also help you determine whether the keto diet is the right eating style for your health needs.

“They can assess your weight loss goals and trajectory and help build a diet for you that will include amounts and types of foods,” she says. “They’ll also help you manage any symptoms and side effects you experience along the way.”