Managing Fatigue on a Keto Diet

Manage Fatigue on Keto Diet


If you are relatively new to the Keto lifestyle and are experiencing one or more of the infamous ‘Keto Flu’ symptoms that include fatigue, the more you understand what can lead to fatigue, the better equipped you will be to manage—or even prevent—it. Here are some of my suggestions:  


Whenever you eat more carbohydrates than you need, your body stores some of the excess in your muscles and liver as a backup source of energy. This stored formed of carbohydrate is called glycogen, and in your body, each gram of glycogen is bound to three times its weight in water. After you start a carb-restricted diet like Keto, your body uses up all its glycogen, and all of that bound-up water is released through urination. This is what it means to ‘lose water weight’. On average, the body of an adult human contains ~60% water. A five to eight percent decrease in total body water can cause fatigue and dizziness. The more weight and body mass that you have, the more water you’ll probably lose—and the more you’ll need to replace. Water losses occurring during the initial stages of nutritional ketosis range from a low of 1-2 pounds to as high as 10-15 pounds in larger individuals.

A good rule of thumb for ensuring adequate hydration is to drink a minimum of three liters of fluid every day during the first week of your Keto Diet, which is actually pretty much in line with The Institute of Medicine’s recommendation that women consume 91 ounces (11+ cups a day) and men consume 125 ounces (15+ cups a day). One thing to note is that too much water intake can flush out electrolytes more quickly, so it is important to replenish those – more on this next 👑

Bottom Line: Dehydration will make just about every ‘Keto Flu’ symptom worse. The recommendation of ‘drink to thirst’, is a good guideline, but it’s important to note that thirst might not be a reliable early indicator of your body’s need for water. As we age, our thirst mechanism starts to decline and, if you’re an older adult, you might not feel thirsty until you’re already dehydrated.


One of the best ways to combat fatigue and Keto Flu symptoms is to increase your electrolyte intake. Some specific electrolytes to focus on are Sodium, Potassium, and Magnesium.


In addition to regulating blood sugar, insulin acts on the kidney to promote sodium reabsorption. Without insulin, sodium passes right through the bloodstream, and the kidneys filter it into urine. The restriction of carbohydrates on a ketogenic diet leads to a drop in the body’s levels of insulin, triggering a decreased reabsorption of sodium along with water. This mechanism offers another explanation why low-carbohydrate diets have a diuretic effect beyond what was described in the first section on hydration.

Since the loss of salt and water is responsible for most ‘Keto Flu’ symptoms, increasing your intake of both can help reduce your symptoms of fatigue significantly. Most of the sodium in your body is found in your bloodstream, so if your body gets deficient, you don’t have many reserves to tap into. There appears to be a discrepancy between the Recommended Dietary Allowance (RDA) for sodium, which is less than 2,300 mg per day, and what is recommended by the ‘Keto’ community. A large number of health experts—and Keto followers—have reason to question this one-size-fits-all RDA recommendation. Lyle McDonald, author of The Ketogenic Diet, recommends that very low-carb dieters supplement their daily electrolyte intake with the following at a minimum:

  • 3-5 grams (3,000-5,000 mg) of sodium chloride (salt)
  • 1 gram (1,000 mg) of potassium
  • 300 mg magnesium

In an effort to offer a more personalized recommendation, an optimal salt intake would depend on several factors, including sodium losses associated with the ketogenic diet (especially in the first few weeks), in addition to any preexisting medical conditions such as kidney disease, high blood pressure, heart or liver problems. In any of these cases, it would be wise to talk to your doctor or healthcare professional before adding more sodium to your diet.

If you make the proper food and meal choices on the Keto Diet you can easily boost your salt intake and meet any increased dietary requirements, without having to take additional sodium supplements. Try seasoning your food/meals with regular iodized table salt, sea salt, or mountain salt and choosing minimally processed salted foods, such as salted nuts & seeds, aged and hard cheeses (blue cheese, sharp cheddar), salted butter, olives, pickles, and bone broth/bouillon.


Just as you lose sodium in the first few weeks of a Keto Diet, the salt depletion causes a parallel loss of potassium, which can cause a host of symptoms, including weakness and fatigue. Although potassium is the third most abundant mineral in your body, very few people consume enough of it. The recommended intake of potassium for adults is 4,700 mg/day. Potassium is easier than most things to overdo, so just be mindful of your intake if you plan on supplementing your diet with pills, electrolyte mixes, etc. Ideally, you should prioritize consuming potassium-rich foods, for which there are an abundance of options on the ketogenic diet. Potassium-rich keto-friendly foods include avocado (1000 mg/medium avocado), spinach (800 mg/1 cup cooked), salmon (500mg/3 oz), whole fat Greek yogurt (450 mg/cup), pumpkin seeds (226 mg/oz), and unsweetened coconut (152 mg/oz).


Aside from the increased urinary excretion of magnesium in the beginning stages of ketosis, another possible contributing factor to low magnesium levels is that of diarrhea-induced magnesium losses, and/or malabsorption due to the high fat content of the keto diet. Since magnesium helps produce and transport energy, an insufficient level can easily result in feeling tired and weak.

Fatigue is actually one of the most common and early symptoms of a magnesium deficiency.

In addition to losses via urine and stool, intense exercise, lack of sleep, and stress can also deplete magnesium levels. As in the case of water, sodium, and potassium, it is unlikely that fatigue will dissipate unless your body gets the right amount of magnesium in its system – maintaining good magnesium levels is also important for managing hair loss and treating constipation if you are in the early stages of adopting the Keto lifestyle. Until your body’s fluid and electrolyte losses stabilize, and/or until your body adapts to a high(er) fat intake, you need to be getting enough magnesium to keep your energy levels where they should be. The Recommended Daily Allowance (RDA) for magnesium intake is 400-420 mg/day for men and 310-320 mg/day for women.

Magnesium-rich foods to enjoy on the Keto Diet include hemp seeds (170 mg/1 oz), sesame seeds (100 mg/oz), almonds, cashews, sunflower and pumpkin seeds (all containing ~75 mg/oz), and dark cocoa powder (50mg/tbsp).

Daily magnesium supplementation may be necessary if you continue to experience symptoms of magnesium depletion despite adequate intake from food/meals. The decision to supplement should ideally be made with the input from your health care team, as magnesium can interfere with a number of prescription drugs, including certain blood pressure medications, statins, and antibiotics. Taking a glycinate or malate form of this mineral might be better tolerated if you have a sensitive stomach, and taking any magnesium supplement with meals can also help to minimize an upset stomach.

Bottom Line: Just as adequate hydration is fundamental for managing fatigue while on a ketogenic diet, it is just as crucial that you replace some of the sodium, potassium, and magnesium that you are eliminating because if these are not replaced, it is likely that you will experience worsening symptoms of fatigue.


Fatigue often results from the sudden drop in carbohydrates, which happens as you begin a Keto Diet. Many Keto followers rightly use the term ‘carb withdrawal’ to describe their symptoms of fatigue. When our bodies are accustomed to using carbs for energy, it takes some time to readjust to using fat for energy. In the beginning, the body may not be well equipped to make this switch. This transition period is another cause of fatigue in the early phase of the ketogenic diet—your body is building up the reserves to start running on fat as it creates more enzymes to more efficiently metabolize fat. The number of fat-converting enzymes gradually increases as you become ‘keto adapted’. Although it usually takes a person between 2-5 days to enter ketosis, it can take much longer to be fully ‘adapted’, which means your body is readily and easily able to convert those fatty acids you’re eating into ketones.

Fat phobia is common among people who venture into a Keto eating style and you’re likely going to need to eat substantially more fat than you’re used to – and that could mean more calories! It might be helpful to keep a food journal for several days to tally up your macronutrient ratio so you can make some adjustments if needed. There are several ‘Keto or Macro Calculators’ available as apps or online that can help determine your macronutrient nutritional profile (ideal ratio of carbs, proteins, and fats), such as: Ruled.Me Keto Calculator. There are also various apps available to help calculate your daily nutritional intake in order to ensure that you are consuming adequate amounts of these macronutrients.

Bottom Line: Too low a calorie (energy) intake can also lead to fatigue. Be sure you aren’t reducing your calorie intake too much. The point is to avoid going both low-carb and low-fat. If you sharply lower your carb intake without upping your fat consumption, your body will think it’s starving. You will feel tired, hungry and miserable—and your weight loss (fat loss) might stall. A well-balanced Keto Diet should include enough healthy fat—and calories—so that you are not hungry after a meal, can go for several hours without eating, and have ample energy.

Woman Boxing


The more you move, the better equipped you are to produce more energy. However, don’t beat yourself up if initially you’re lacking energy, have no motivation for exercise or can’t perform during your workouts. You might initially need to reduce your exercise load and hold off on high-intensity exercise until you no longer feel fatigued or weak. Interestingly, research studies found those who complained of fatigue or tiredness actually increased their energy levels with regular low intensity exercise like walking. Furthermore, when you sit or lie down for too long, your blood vessels have a tendency to constrict, which further reduces energy levels. Whatever exercise you choose encourages oxygen-rich blood to pump through your body to the heart, muscles and brain, making you feel more alert and less tired!

Bottom Line: 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, helping with sleep, boosting your mood, using up some circulating ketones, and helping you get through this rough period.


Most people take caffeine to help them perk up – and we know how much the Keto community loves their (Bulletproof) coffee. In moderation, caffeine does improve alertness and energy. However, too much caffeine can cause jitteriness, increased heart rate or palpitations, anxiety, and insomnia. In addition, after caffeine wears off, caffeine consumers can ‘crash’ and feel fatigued. Caffeinated beverages, such as hot cocoa and tea, should be consumed no later than mid-afternoon, as the stimulant effect of caffeine can last up to several hours.


One of the possible side effects of a ketogenic diet is temporary insomnia, which can last from a couple of days to over a month. It will resolve with time, as your body gradually gets ‘fat-adapted’. In the interim, it can definitely take a toll on your energy level and, in return, negatively impact your weight loss or other wellness goals. To optimize the quality of your sleep you can start by ensuring an adequate fluid and electrolyte intake, as one of the side effects of an electrolyte imbalance is restlessness and insomnia. It might help to take half of your daily dose of magnesium at bedtime. As mentioned earlier, one of the benefits of magnesium is its calming effect on the nerves. In addition, if your sleep is interrupted by leg muscle cramping, magnesium would also be beneficial, as it plays a key role in the proper functioning of muscles.

To help improve your odds at a good night’s sleep, try minimizing any stressors in the evening. Make a concerted effort to ‘unwind’ from the events of your day by establishing a relaxing pre-bedtime ritual. This includes limiting your exposure to electronics an hour before bedtime. Not only can your computer, cell phone or other device keep your brain on ‘wired’ mode, their screens emit ‘blue light’, which can interact with your body’s natural production of melatonin, a sleep-inducing hormone. Also do your best to keep to a sleep schedule. A routine of getting to sleep and waking up around the same time can help to regulate your body’s clock and can help you fall asleep and stay asleep for the night.

Final Thoughts

The assorted symptoms, including fatigue, that one often experiences in the beginning stages of the Keto Diet usually last several days, but can sometimes stick around for a month or more. You can help overcome—or minimize—fatigue by staying hydrated, getting enough electrolytes (sodium, potassium, and magnesium), eating enough calories and fats, limiting caffeine, and focusing on getting adequate sleep and rest. If none of these strategies work for you, it might be a good idea to check with your healthcare team regarding other possible reasons for your fatigue, as there could be an issue with anemia, a hormonal irregularity, or another health condition that merits medical attention.


Lauren Paley

Creator of Fearless Keto. Model + health & wellness enthusiast. After losing 45 pounds on Keto, I want to give back to the community that gave me so much 👑

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