When you cut carbs your body sheds water and, with it, sodium, potassium and magnesium. Replacing them is what actually fixes the keto flu. Here are sensible daily targets. See also electrolytes on keto.
Sodium is the big one and the fastest fix for keto flu. Salt your food generously, and a cup of broth is an easy way to top up.
Cutting carbs lowers insulin, and low insulin tells your kidneys to let go of sodium and water. The first week or two of keto is largely water leaving, and it takes potassium and magnesium out with it. That flush is what causes the headaches, fatigue and leg cramps people call the keto flu, and topping up the three minerals is what fixes it rather than waiting it out. Sodium matters most and works fastest, so salt your food, sip broth, and reach for potassium and magnesium from food where you can. The full playbook is in getting electrolytes right on keto, and if you are in the thick of it now the keto flu guide walks through the symptoms.
How much sodium on keto?
Roughly 3000 to 5000mg a day, more with heavy sweating: about one and a half to two teaspoons of salt across the day.
What fixes the keto flu?
Sodium first, then potassium and magnesium. Salt and broth usually turn it around within a day or two.
How much potassium and magnesium?
About 3000 to 4000mg potassium and 300 to 400mg magnesium, ideally from food rather than large supplement doses.
General daily targets for a healthy adult on a low-carb diet, not medical advice. Keto raises sodium needs well above the usual "eat less salt" advice, because low insulin makes your kidneys excrete more of it. If you have high blood pressure, kidney disease, or take medication that affects electrolytes (including diuretics), talk to your doctor before loading up on salt or potassium. Potassium supplements in particular can be risky in large doses, so get it from food where you can.