When you cut carbs sharply, your body adjusts. Some people notice nothing. Others feel a short stretch of tiredness, headache, brain fog, irritability, muscle cramps or lightheadedness. People often call this the “keto flu,” though it is not an infection.
Why it may happen
Your body stores carbohydrate as glycogen, and each gram holds a few grams of water. When glycogen drops, you lose water, and with it sodium, potassium and magnesium. That shift is a likely contributor to the early symptoms. Eating too little overall can make things worse.
What people commonly find helpful
- Drink water throughout the day.
- Salt your food to taste, and consider sipping broth. If you have high blood pressure or kidney disease, ask your doctor first.
- Eat potassium- and magnesium-rich foods: spinach, avocado, almonds, pumpkin seeds, salmon and leafy greens.
- Eat enough. Do not cut calories at the same time as carbs.
- Rest and go easy on intense exercise for a few days.
- Add fiber with non-starchy vegetables, chia or ground flax if constipation appears.
About supplements
Some people use electrolyte supplements. Please talk to your doctor before taking potassium or magnesium supplements, particularly if you have kidney problems or take blood pressure medication. These minerals can cause problems in the wrong circumstances.
How long does it last?
For many people it fades within a few days to two weeks.
When to stop and call a doctor
Seek medical advice if you have severe dizziness or fainting, a racing or irregular heartbeat, persistent vomiting, confusion, extreme thirst or urination, or any symptom that worries you. If you take insulin or medication for diabetes or blood pressure, speak with your doctor before cutting carbs.
For a printable troubleshooting chart, see the Black Tie Pantry Guide in the bundle.