Low-carb diets like keto are extremely popular, but some people complain they get dizzy on keto, especially when they're first starting out. Here's why the lack of carbs on a ketogenic diet may cause a feeling of lightheadedness — and what you can do about it.
One of the primary goals of the keto diet is to put your body in a state of nutritional ketosis — that's when you're burning fat for your primary fuel source instead of carbs, according to a review published in September 2018 in Current Nutrition Reports. Nutritional ketosis is generally safe for most people, the review states, but it can come with some noticeable side effects, dizziness in particular.
The collection of dizziness and other symptoms like headache, fatigue, nausea and even brain fog have been called the "keto flu," according to Harvard Health Publishing, although this isn't an acknowledged medical condition. The symptoms tend to start within a few days of being on the diet.
Read more: Negative Side Effects of a Low-Carb Diet
Electrolyte and Fluid Imbalances
As you transition into ketosis, your body burns through your glycogen stores, the back-up supply of carbs that are stored in your muscles and liver, according to a May 2018 study in the Journal of Nutrition and Metabolism. These carbs are stored with large amounts of water, which contain electrolytes such as potassium and sodium that help to regulate your body's fluid balance.
As you burn through your glycogen stores, all of the water and electrolytes they contain are flushed out through your urine. This can cause dizziness, according to Jean LaMantia, RD, a registered dietitian in private practice in Toronto. "if you aren't drinking enough, or not adding enough salt to your diet, or both."
These fluid losses can easily lead to dehydration — you'll feel it as extreme thirst, dry mouth, dry skin, fatigue and dizziness, according to the U.S. National Library of Medicine.
Additionally, electrolyte losses may also cause dizziness because they can lower your blood pressure, says LaMantia. When there are huge shifts in electrolyte levels, such as those that occur when you first start keto, you're likely to get those keto flu symptoms, which might also include headache, foggy brain, fatigue, nausea and constipation, among others, notes Harvard Medical School.
Low Blood Sugar Levels
Another reason that low-carb diets may cause dizziness is because of changes in your blood sugar levels. LaMantia explains, "When you start on a low-carb diet, the level of sugar in your blood will reduce … It's possible your body could respond to this with low blood sugar."
According to the American Diabetes Association, one of the signs of a low blood-sugar level is dizziness, along with shakiness, nervousness, sweating, confusion, increased heart rate and hunger. Low blood-sugar levels can be dangerous, especially in people with diabetes. If you have type 1 or type 2 diabetes, you should speak to your doctor before starting a low-carb or keto diet, especially if you're taking any blood-sugar lowering medications, such as metformin or insulin.
Avoiding Keto Dizziness
One way to sidestep or at least minimize dizziness on low-carb or keto diets is to stay adequately hydrated. According to the Cleveland Clinic, you should make an effort to drink water regularly and avoid beverages that tend to be dehydrating, such as those with caffeine, sugar and/or alcohol. You should be drinking enough for your urine to be clear or pale yellow in color.
Water intake requirements vary, says the National Academy of Sciences. Men need about 13 cups of fluids a day (including water and other beverages), while 9 cups a day should do it for women.
Additionally, according to LaMantia, if you tend to experience low blood sugar, proceed more cautiously with a low carb diet. She suggests easing into the diet slowly, rather than suddenly decreasing your carb intake.
Read more: Low-Carb Diet and Exercise
- American Diabetes Association: “Hypoglycemia (Low Blood Sugar)”
- Cleveland Clinic: “Dehydration”
- Current Nutrition Reports: “Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome”
- Harvard Health Publishing: “What Is Keto Flu?”
- Journal of Nutrition and Metabolism: “The Effect of Medium Chain Triglycerides on Time to Nutritional Ketosis and Symptoms of Keto-Induction in Healthy Adults: A Randomised Controlled Clinical Trial”
- Jean LaMantia, RD, registered dietitian, Toronto
- U.S. National Library of Medicine: “Dehydration”
- National Academy of Sciences: "Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005) Chapter: 4 Water"