Quick answer: Keto flu is a set of temporary symptoms some people feel in the first days to weeks of a ketogenic diet, such as fatigue, headache, dizziness, irritability, brain fog, nausea and muscle cramps. It isn’t an infection. It’s linked to fluid and electrolyte losses and the body adjusting to burning fat. Hydration, electrolyte-rich foods and easing into keto usually help.
Symptoms
- Fatigue
- Headache
- Dizziness
- Irritability
- Brain fog
- Nausea
- Muscle cramps
Why it happens
Fluid and electrolyte shifts
As glycogen is used up, water is released, and lower insulin makes the kidneys excrete more sodium. Potassium and magnesium can drop too. See balancing electrolytes.
Switching fuel sources
There can be a lag while your body ramps up making and using ketones. See what is ketosis.
Carbohydrate withdrawal
Cutting sugar and refined carbs abruptly can bring cravings and irritability.
How to ease it
- Drink water steadily through the day
- Eat electrolyte-rich foods: leafy greens, avocado, nuts, broth
- Ease in by lowering carbs over a week or two
- Rest, sleep and keep exercise gentle at first
- Avoid common keto mistakes
When symptoms aren’t keto flu
Symptoms that are severe, last more than a couple of weeks, or include vomiting, confusion or a racing heart need medical attention, especially if you have diabetes.
Healthy aging lens
Older adults and people on blood pressure medication or diuretics are more prone to electrolyte problems, so build up slowly and check with your provider.
When to see a naturopathic doctor
- You have diabetes or take insulin, sulfonylureas or SGLT2 inhibitors (risk of low blood sugar or ketoacidosis)
- You take blood pressure medication or diuretics
- You have kidney, liver, gallbladder or pancreas disease, or high cholesterol
- You are pregnant, breastfeeding, or have a history of disordered eating
- You want a keto plan tailored to your labs and goals
See a medical provider promptly for nausea and vomiting, abdominal pain, confusion, fruity-smelling breath with rapid breathing, or very high blood sugar or ketone readings, which can signal ketoacidosis.
Want a keto plan that’s safe for your health?
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Frequently asked questions
What is the keto flu?
Temporary symptoms while the body adapts to keto.
How long does keto flu last?
Usually a few days to a couple of weeks.
How do I get rid of keto flu?
Hydrate, get electrolytes from food and ease in.
Is keto flu dangerous?
Usually not, but severe or lasting symptoms need medical care.
Sources
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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