You’ve read about all the benefits: weight loss, reduced appetite, improved energy and mental clarity. But now that you’ve actually gotten started with the ketogenic diet (or “keto”), you find yourself feeling worse than you did before. What gives?
This is not an uncommon scenario. Unfortunately, these keto diet side effects or “keto flu” symptoms that are bad enough can scare a lot of people away (and who will then ever reap those very real benefits).
But the good news is that you won’t feel uncomfortable forever while on the ketogenic diet. For most people, side effects of ketosis tend to go away within several weeks — especially if you take certain precautions like preventing dehydration and eating the right foods.
What Is the Keto Flu?
“Keto flu” is a term that some people use to describe common ketogenic diet side effects. Why do you get the keto flu? Because while ultimately the ketogenic diet is both safe and health-promoting in many ways, it forces your body to go through some major changes. (1, 2) One of these is basically a withdrawal from sugar and carbohydrates. Keto alters your metabolism in a way that turns you from a “sugar burner” to a “fat burner.”
Transitioning into the metabolic state of ketosis, in which you produce ketone bodies that are responsible for many of the health benefits of the ketogenic diet, can initially cause some side effects as your body acclimates to using fat instead of glucose for fuel. You might feel fatigued because you’ll likely spend some time in an “in between phase,” in which you’re not totally using glucose or ketone bodies effectively for energy.
Think about it: This is probably the first time in your whole life that you’ve severely cut off your body’s supply of glucose. So it’s not surprising that you’ll feel some effects. The bacteria in your microbiome will also experience some changes during ketosis, so this can temporarily affect digestion.
Can you avoid the keto flu? Yes and no. Not every person will experience keto flu symptoms; it really all depends on your overall health before starting the diet, the types of foods you eat while beginning the keto diet and other factors —like if you have nutrient deficiencies, your gender, age, activity level, sleep, stress and genetics.
If you ate a pretty high-carb, high-sugar diet before starting keto, chances are you’ll experience more keto flu symptoms. You can lower the odds you’ll suffer from keto side effects by following the diet correctly and eating healthy sources of fats (i.e, unprocessed and whole foods) and other nutrients — especially B vitamins and electrolytes.
Normally if someone is otherwise healthy before starting the keto diet, they will be able to bounce back quickly and start seeing results. But for someone who already has a serious metabolic condition, such as diabetes or renal insufficiency, then it’s best for them to be monitored by a doctor and to carefully look out for warning signs of a negative reaction to ketosis (such as severe symptoms that last more than about a week). (3)
Keto Diet Side Effects & Keto Flu Symptoms
- Exhaustion/low energy
- Cravings for carbs and sugar
- Loss of appetite
- Bad breath
- Heartburn or other symptoms of indigestion
- Low motivation to exercise and poor recovery from workouts
- Low libido
- Muscle aches or weakness
- Brain fog
- Trouble sleeping
- Moodiness or irritability
- Rarely, a small percentage of people (including children following keto diet) may experience vomiting, high cholesterol, kidney stones, growth slowing, and severe gastrointestinal upset. (6)
When do keto diet side effects/keto flu symptoms usually start? Typically within several days of starting the ketogenic diet. Your body will use up stored glucose within a couple days, at which point it will go searching for another fuel source if you aren’t eating any more carbohydrates.
This is when ketosis begins and ketone bodies will start to be produced, assuming you are fasting or eating a high enough percentage of fat. Once you’ve become “keto adapted,” you shouldn’t struggle with keto side effects anymore. You’ll be able to transition into and out of the diet more easily without feeling like a train wreck.
How to Overcome the Keto Flu & Other Keto Side Effects
How long does it take to get over the keto flu? Keto diet side effects usually clear up within about 1–3 weeks, although some people with struggle with symptoms for up to six weeks (especially if they aren’t following the diet correctly).
Here are tips that can help reduce keto flu symptoms (aka side effects associated with the ketogenic diet):
1. Focus on Alkalizing Foods
The ultimate goal of following the keto diet should be to feel better and get healthier. In order to do this, you need to adopt alkaline diet principles, which help to reduce inflammation, restore your nutrient stores and balance your body’s pH level. What types of foods are alkalizing?
- Fresh vegetables (especially those that are green). Good choices include: leafy greens, avocados, mushrooms, radish, artichokes, alfalfa grass, barley grass, cucumber, kale, jicama, wheat grass, broccoli, oregano, garlic, ginger, green beans, endive, cabbage, brussel sprouts and celery.
- Try to include some raw foods in your diet to boost your enzyme intake. A great way to do this is to try vegetable juicing, or only lightly steaming vegetables.
- Apple cider vinegar.
- Alkaline water, which has a pH of 9 to 11. Shake things up by adding some lemon or lime to your water.
- Green drinks. Drinks made from green vegetables and grasses in powder form are loaded with alkaline-forming foods and chlorophyll.
- Limit or give up caffeine. Avoid sugary drinks and keep alcohol intake low (such as having one glass of low-sugar wine per day or less).
- Avoid eating inflammatory, processed foods that are filled with additives/synthetic ingredients. Also try to limit “low-carb foods” that are still unhealthy and difficult to digest. These include: processed meats like cold cuts,(especially pork), hot dogs, cured meats, bacon, processed cheeses, refined vegetable oils, processed nut butters and most bottled salad dressings.
2. Make Sure You’re Eating Enough Fat and Calories
Staying in ketosis requires getting about 80 percent of your daily calories from sources of fat. Examples of healthy keto-friendly fats that you should fill up on include coconut oil, real olive oil, MCT oil, grass-fed butter, ghee and fattier cuts of meat. You should only be getting about 15 percent of daily calories from protein and only around 5–10 percent from carbohydrates.
If you veer off too much from these guidelines, chances are you won’t actually ever get into or stay in ketosis. And this is when you’d be most likely to experience symptoms like low energy and brain fog. That’s because you won’t be producing ketone bodies that supply the brain and body with energy.
The solution? Make sure you’re eating enough fat, but not too much protein or carbs. You may need to keep a food journal for several days to tally up your macronutrient ratio so you can make some adjustments if needed. Remember that you’re likely going to need to eat substantially more fat that you’re used to — and if you don’t eat enough, you won’t be giving your body enough fuel. You might also want to take an exogenous ketone supplement for the first week or two of the diet to help raise ketone levels in your blood and provide you with more energy.
You should consume even more fat if you’re feeling hungry and weak. But if you eat too much protein, some of the amino acids can be converted into glucose, which is why the ketogenic diet is not a high-protein diet like many other low-carb diets.
Finally, make sure you’re not chronically in a calorie deficit from eating too little calories in general. This can also contribute to cravings, moodiness, fatigue, poor concentration and other side effects.
3. Stay Hydrated
Dehydration will make just about every keto flu symptom worse. Drinking enough water is especially important if you experience keto flu symptoms like vomiting or diarrhea, since these cause you to lose fluids.
In addition to eating hydrating foods (like vegetables, bone broth smoothies or green juices), also try to drink a glass of water every 1–2 hours. If your urine is dark yellow, this means you need to drink more water!
4. Consume Enough Salt and Prevent Electrolyte Imbalance
Electrolytes such as magnesium, potassium and sodium can be lost at an higher rate during ketosis due to the kidneys flushing out sodium and increased urination, which is one reason why most people lose a lot of “water weight” quickly on the ketogenic diet. If you aren’t careful about replenishing electrolytes, this can contribute to symptoms like weakness, cramps, headaches and constipation.
How can you get electrolytes? To prevent keto flu muscle aches and other side effects, consider taking a magnesium supplement before bed. You’ll also benefit from having some bone broth daily which provides electrolytes and trace minerals.
Many people find that including more salt in their diet also helps reduce keto flu symptoms (this is why some add bouillon cubes to water to make a quick broth). I recommend adding some real sea salt to your meals, such as sprinkling some on eggs and veggies, as well as drinking 1–2 cups of bone broth.
5. Eat Enough Fiber
To help prevent symptoms like constipation and diarrhea, make sure to include some high-fiber keto friendly foods in your diet, especially vegetables. Even though the bulk of your calorie intake will be from fats, vegetables should still be included in just about every meal you have while on the keto diet.
- All non-starchy vegetables, especially leafy greens, peppers, cruciferous veggies like broccoli or cauliflower, mushrooms, asparagus, zucchini, artichokes, etc.
- Avocado, which is a great source of fat, potassium and fiber.
- Coconut flakes/coconut flour, another high-fat source of fiber.
- Seeds and nuts. What nuts are OK on keto? In small-to-moderate amounts, almonds, walnuts, cashews, pistachios and brazil nuts can all be eaten, since they are all good sources of fiber and trace minerals (I don’t recommend peanut/peanut butter because they tend to carry mold). You can also use almond meal/almond flour in place of regular flour. Seeds that supply important nutrients include sesame, sunflower, chia, flax and pumpkin seeds.
6. Have Foods High in B Vitamins
B vitamins (like vitamin B12, thiamin, riboflavin and niacin) are important for energy production, cognitive health and many metabolic functions.
A great way to get more B vitamins easily is by having 1–2 tablespoons of nutritional yeast everyday. Other foods high in B vitamins include: organ meats like liver, grass-fed meat, salmon, pastured eggs, pastured poultry, and vegetables.
7. Rest, Relax and Recover
Don’t beat yourself up if initially you’re lacking energy, have no motivation for exercise or can’t perform during your workouts. You’ll probably need to initially reduce your exercise load until you feel better. Make sure to get plenty of sleep every night (7–9 hours ideally) and to take breaks to relax during the day.
If it helps you feel better, stick with lighter forms of exercise during the beginning phase of the keto diet, such as walking outdoors, yoga or light cycling. These can also be great for reducing stress and helping you get through this rough period.
You can hold off on high-intensity exercise until you no longer feel fatigued, weak and dizzy. That being said, some people feel better while struggling with the keto flu if they do some type of exercise, since this can lift their mood, help with sleep and use up some circulating ketones.
Final Thoughts on Keto Flu Symptoms
- “Keto flu”is a term that some people use to describe common ketogenic diet side effects. Keto flu symptoms can include: weakness, fatigue, moodiness, cravings, brain fog and digestive issues.
- Side effects of the keto diet usually last several weeks, but can sometimes stick around for a month or more.
- You can help overcome keto flu symptoms by: eating alkalizing foods, eating enough fat and calories, making sure to get enough fiber, staying hydrated, and focusing on getting enough rest, electrolytes and B vitamins.