The Keto Flu: Symptoms, Remedies and How to Avoid It

The ketogenic diet is an increasingly popular option for people looking for a natural way to lose weight and burn fat. In certain cases, the diet–which is low in carbohydrates, high in healthful fats, and moderate in protein–can even be used to help manage a variety of chronic illnesses, including heart disease, diabetes, and obesity.

However, when people begin researching the ketogenic diet, one of the first phrases they encounter is a pretty scary one: “the keto flu.”

While the keto flu is one of the most dreaded side effects of the ketogenic diet, it is actually a sign that you’re on the right track! The condition is a direct consequence of reducing carbohydrates and transitioning your body into a state of ketosis, and there are a number of steps you can take to mitigate its severity–or prevent it entirely.

What Is The Keto Flu?

The keto flu, which is not actually a “flu” at all since it’s not viral in nature, is a constellation of symptoms that often accompany the first days or weeks of a ketogenic diet. Symptoms include fatigue, headaches, brain fog, muscle cramps, dizziness, nausea, and lethargy.

There is high variability among individuals both in the incidence and severity of these symptoms, which is thought to be driven by differences in individuals’ metabolism as well as their diet pre-adherence to the ketogenic diet. It’s easy to see how this is one of the most commonly cited reasons why people abandon keto: they start the diet, feel terrible almost immediately and shortly thereafter decide that the ketogenic diet is not for them.

However, it is our hope that a better understanding of this condition and how to manage it will help empower new adherents to stick with the diet and reap its long-term benefits.

Keto Flu Symptoms

• Fatigue
• Headaches
• Brain fog
• Muscle cramps
• Dizziness
• Nausea
• Lethargy

For the average person, carbohydrates have been the cornerstone of their diet since the day they were first introduced to solid food by their parents.

In fact, many nutritional guidelines today suggest we consume anywhere from 40-60% of our total daily calories from carbohydrates. Unfortunately, these carbohydrates are often derived from high-processed junk food and refined sugars with low nutritional quality. 

Even if the carbohydrates you consume are from a relatively healthful source–think quinoa or other ancient grains–these foods still trigger the release of higher levels of insulin than any other macronutrient, so they wreak havoc on blood sugar levels. The exact metabolic impact of carbohydrates varies by person, but the latest scientific research continues to support the notion that most Americans would be well-served to reduce carbohydrate intake.

While it’s a complex pathway, the keto flu is largely driven by two forces unique to the ketogenic diet: a reduction in overall electrolyte intake and the diuretic nature of the diet. As mentioned above, most people consume more carbs by calorie content than any other macronutrient, and most of those carbs come from low-quality, processed sources.

Ironically, when we remove these foods from our diet, we actually precipitously decrease our overall sodium intake. And since sodium is an electrolyte, this can lead very quickly to an electrolyte deficiency and trigger the keto flu.

Second, as you cut carbohydrates out of your diet and move your body towards ketosis, insulin levels drop, signaling the kidneys to release water and vital electrolytes like sodium and potassium. This molecular pathway is what makes the ketogenic diet diuretic in nature; the sudden drop in insulin triggers the kidneys to release water and electrolytes through increased urine production.

While the keto flu is a completely normal reaction to the ketogenic diet, there are long-term risks to not addressing the condition. In all likelihood, symptoms will persist until you address them, so they could last over the entire life of the ketogenic diet if you don’t take action. Sounds miserable!

The keto flu can also lead to sleep disturbances and an elevated heart rate, which is a side effect of your body’s attempts to retain sodium through the release of adrenal hormones.

Finally, if left untreated for a long period of time, the keto flu could lead to bone mineral loss or osteoporosis. Our bones are one of the core areas where we store sodium and, if the keto flu is left unchecked, your body could start to leach calcium, along with sodium, from your bones.

Risks of Electrolyte Deficiency on a Ketogenic Diet

• Sleep disturbances
• Elevated heart rate
• Mineral loss
• Osteoporosis

While the keto flu is the body’s natural reaction to a ketogenic diet, suffering from it is not a foregone conclusion. You can dramatically reduce the symptoms of the keto flu—or even avoid them altogether—by properly supplementing your electrolytes as you transition into ketosis.

If you find yourself to be especially sensitive to the ketogenic diet, you can also ease your transition into ketosis by slowly reducing carbohydrates rather than going cold turkey on day one.

Remedies for the Keto Flu

Replacing the electrolytes your body has lost is the single most important thing you can do to combat or prevent the symptoms of the keto flu. This means ensuring you consume adequate levels of sodium, potassium, and magnesium either from food sources or through supplementation.

We will address exactly what we mean by “adequate levels” in a moment, but for now, we’d like to propose some simple ways to increase your intake of electrolytes:

1. Salt Your Food

Salt your food. Even if it feels weird or gustatorily challenging to salt a salad, try it. It’s critically important that you increase salt consumption on the ketogenic diet, as most of the foods on the menu will not have naturally-occurring sodium at adequate levels. Any kind of table salt will do, but if you have a personal preference for one type over the other, no problem! Just salt your food.

However, it’s also important to remember that sodium is not the only electrolyte that needs to be kept in balance on a ketogenic diet. Magnesium and potassium are both critically important electrolytes that we should pay attention to as well.

Fortunately, a well-formulated ketogenic diet that is high in healthful fats and plant-based foods often provides enough of these two electrolytes. Specifically, magnesium can be derived from avocados, almonds, bananas, and leafy greens, while sweet potatoes, spinach, butternut squash, and beets are all great sources of potassium.

2. Consume Bone Broth

There is a robust body of scientific research that has identified bone broth as an incredibly healthy, nutrient-packed superfood. Bone broth is made by simmering the bones and connective tissues of an animal for a long period of time—generally between ten and twenty hours—which is what separates it from the standard broth or stock found in most grocery stores.

Cooking for such an extended period of time allows the broth to absorb the collagen, glutamine, and other minerals that give bone broth its rich nutrient density that is commonly touted for its benefits for the gut, joints, skin, and overall health.

Furthermore, while bone broth is a decent source of sodium on its own, it’s very easy (and recommended) to add salt or a bouillon cube to turn it into a keto flu-busting intervention.

3. Make Electrolyte Homebrews

You should never turn to sugary sports drinks to combat the keto flu. Unfortunately, all of the traditional electrolyte products on the market have insufficient levels of actual electrolytes and are very high in sugar. This sudden burst of electrolyte-less sugar will spike insulin levels and derail your path to ketogenesis.

Despite their catchy marketing campaigns, endorsement deals with famous athletes, and sponsorships of virtually every visible sporting event, these drinks are not your friend and should be avoided regardless of whether or not you adhere to a ketogenic diet.

This is why I spent years mixing up homebrew concoctions with ingredients from my own pantry. With some trial and error, I was able to design a few great do-it-yourself drink recipes for those who are more inclined to mix up their own keto flu-killing concoctions. If you’d like to give some of these a try, you can see a list of my favorite recipes here.

4. Drink LMNT Recharge

After years of tinkering with homebrew recipes—some of which were way off the mark!—and waiting for someone to develop and release an electrolyte product that wasn’t bathed in sugar, I finally decided to do something about this problem.

Thus was born LMNT Recharge, a product that I specifically formulated to help replenish the body’s electrolytes in the initial phase of the ketogenic diet. It’s a tasty electrolyte mix filled with everything you need and nothing you don’t—namely, sugar.

How Much Sodium Is Too Much Sodium?

For the last three decades, we’ve all been told that we need to reduce sodium intake to control blood pressure, and current recommendations call for 1.5 to 2.3 grams of sodium per day.

However, a 2011 study published in the Journal of the American Medical Association painted a much different picture of sodium consumption. This study, which sought to correlate sodium intake with cardiovascular incidents like strokes and heart attacks, found that the lowest rate of these events actually occurred in people consuming five grams of sodium per day. That’s more than double the recommended daily intake!

Furthermore, an individual had to consumer eight grams of sodium per day to reach the same problematic levels of cardiovascular events as those people consuming less than 2 grams of sodium per day.

Another study published in Preventive Medicine found that individuals who restricted sodium intake to less than 2.5 grams per day actually had a higher blood pressure than those who consumed more, further disproving the deep-seated notion that high levels of sodium intake are bad for cardiovascular health.

An individual’s level of optimal sodium intake is a multifactorial question, depending on their age, body mass, their level of activity, and even the region of the world where they live. Without prescribing generic ranges, I think we can undoubtedly say that increasing sodium intake, especially in people who are adhering to a ketogenic diet, is perfectly safe.

The keto flu is an unfortunate side effect of cutting carbohydrates and transitioning your body’s primary fuel source from glucose to ketones. However, it should not deter you from giving this revolutionary diet a try. Your body is perfectly capable of using ketones for fuel, as is the goal of a ketogenic diet, but years of dependence on carbohydrates has forced your body to “forget” how to power itself with fat.

You simply have to give your body time to relearn this natural process. Furthermore, balancing your electrolytes, especially in the early days of your transition into ketosis, will boost your energy levels, eliminate keto leg cramps, and enhance performance and recovery. With an understanding of what the keto flu is and how to prevent and combat its symptoms, we think you will be fully prepared to adapt to this new lifestyle.

Robb Wolf

Robb Wolf, author of The Paleo Solution and Wired to Eat, is a former research biochemist and one of the world’s leading experts in Paleolithic nutrition. Wolf has transformed the lives of tens of thousands of people around the world via his top ranked iTunes podcast and wildly popular seminar series.