What Is The Keto Flu? Symptoms, Causes And Remedies (2024)

Since the keto diet involves removing the majority of carbohydrates from your diet, you may undergo a sort of “carbohydrate withdrawal,” which is what’s referred to as the keto flu, says Priyanka Hennis, M.D., a family physician in Phoenix, Arizona.

When you consume very few carbohydrates, you’re forcing your body into a state of ketosis, explains Roach. “Carbs are the body’s main and preferred source of fuel. When the body doesn’t have carbs to burn, it will instead burn fat, which is what results in increased ketone levels. Ketosis is a metabolic state characterized by raised levels of ketones in the body,” she says.

Initially, entering ketosis can cause quite a few unpleasant side effects.

Symptoms of the keto flu typically start two to seven days after beginning a ketogenic diet, says Mary Wirtz, a Colorado-based clinical registered dietitian and board-certified specialist in sports dietetics. “Symptoms can feel quite similar to the influenza virus,” she says, and they can vary from person to person. Possible symptoms include:

• Headache
• Fatigue
• Nausea
• Vomiting
• Dizziness
• Insomnia
• Diminished exercise performance
• Constipation
• Bad breath
• Irritability
• Loss of focus
• Low energy
• Muscle cramps

Who Is Likely to Get the Keto Flu?

Keto flu symptoms are quite common in individuals who are beginning a ketogenic diet, says Wirtz, and they can be worse if the person isn’t staying well hydrated.

But not everyone who tries a keto diet will experience keto flu symptoms, says Roach—it really depends on the individual.

The exact cause of the keto flu is unknown, but experts have a few ideas. “It may be related to the body adjusting to the low-carb diet, which can be associated with sugar withdrawal and changes to the gut microbiome,” says Roach.

Genetics, dehydration and substantially changing the quality of your diet in a relatively short period of time are factors that may play a role in the onset of keto flu symptoms as well, says Wirtz.

If you decide to try the keto diet, it’s a good idea to work with a registered dietitian to ensure you’re following protocols in a safe manner, adds Roach.

How Long Does It Last?

Keto flu symptoms may resolve themselves in a matter of days, but they can also persist for several weeks. “In most people, symptoms typically get better in 10 days; however, if headaches, fatigue, cramps or irritability last longer than that length of time, it’s a good idea to see your doctor,” says Dr. Hennis. Electrolyte imbalances (which can occur when starting a keto diet) can cause a lot of severe symptoms, but they can also be evaluated through doctor-recommended blood tests and managed accordingly, she adds.

If you’re planning to try a keto diet, here’s a handful of steps you can take to minimize your chances of experiencing keto flu symptoms (or reduce their severity).

Decrease Your Carb Intake Slowly

Instead of cutting nearly all the carbohydrates out of your diet immediately, reduce them gradually over a longer period of time to help reduce symptoms, suggests Roach.

Stay Hydrated

At baseline, most women should aim to consume 2.7 liters (11.5 cups) of fluids daily, and men should try to drink 3.7 liters (15.5 cups) of fluids a day, says Wirtz. Remaining well-hydrated can help prevent headaches and increase energy levels.

Supplement With Electrolytes

It’s easy to develop an electrolyte imbalance with any type of diet, says Dr. Hennis, which can lead to muscle cramps, nausea and more. Supplementing your diet with magnesium, potassium and sodium can help. She recommends trying a sports drink or electrolyte-enhanced water.

Consume Caffeine in Moderation

Too much caffeine can interfere with your sleep, says Roach. Limiting your intake of caffeine can help reduce bothersome symptoms like insomnia, fatigue, irritability and more.

FEATURED PARTNER OFFER

Partner Offers feature brands who paid Forbes Health to appear at the top of our list. While this may influence where their products or services appear on our site, it in no way affects our ratings, which are based on thorough research, solid methodologies and expert advice. Our partners cannot pay us to guarantee favorable reviews of their products or services

Get $50 Off using code FORBES50 at checkout

Nutrisense Continuous Glucose Monitoring Program

• Get invaluable, real-time data about your blood sugar response to food, exercise and sleep
• Personalize your diet by choosing foods with minimal glucose impact
• Distinguish between mental cravings and physical needs for food
• Optimize your metabolism with data insights and personalized dietitian support

Get Started

On Nutrisense's Website

Limit Strenuous Physical Activity

As your body adjusts to the state of ketosis, you may feel weak or fatigued, so stick with light, energizing activities during this period of time, suggests Dr. Hennis. Save the long runs and heavy lifting for when you’re back to feeling your best.

Eat Plenty of Vegetables

Wirtz recommends including a wide variety of non-starchy vegetables (which have fewer carbohydrates) in your diet to help minimize digestive issues that often come with the keto flu. Spinach and other leafy greens, broccoli, cauliflower and Brussels sprouts are all great options. Plus, each of these foods is rich in essential electrolytes.

Stick With It

If you’re becoming discouraged by keto flu symptoms but they’re manageable, Dr. Hennis recommends sticking it out. “Once you start, commit to at least three months of doing the work,” she says. “It usually takes 21 days for any new habit to stick, so practice every day.”