Headache, tiredness, cramps, dizziness, brain fog. The famous “keto flu” is rarely about carbs at all. It is about minerals. Within days of cutting carbs, your body flushes out sodium and water, and potassium and magnesium often follow. The fix is not pushing through; it is replacing what you lost. This calculator gives you daily targets for all three electrolytes, matched to how long you have been on keto and how much you sweat, and it starts with a safety question most calculators skip, because for some people, standard keto electrolyte advice is genuinely dangerous.
Keto Electrolyte Calculator
Work out your daily sodium, potassium and magnesium targets on keto, the minerals behind most "keto flu" symptoms.
These ranges are the ones commonly recommended for keto by low-carb researchers such as Phinney and Volek, and popularised by diet programmes like Virta, they are general information, not a personal prescription. Potassium in particular should come mostly from food. If symptoms persist despite fixing electrolytes, see a doctor.
Why Keto Drains Your Electrolytes
Insulin does more than manage blood sugar. It also tells your kidneys to hold on to sodium. Eat very few carbs and insulin falls, so the kidneys release sodium, and water goes with it. That is the rapid “water weight” loss of the first keto week, and it is also why you can feel dreadful while doing everything else right. Potassium and magnesium drop too: you have cut the foods that supplied them (fruit, beans, grains), and low sodium makes the body waste potassium faster. The result is a mineral problem with a mineral solution.
The Three Minerals That Matter
| Mineral | Typical keto range | What low levels feel like | Best keto food sources |
|---|---|---|---|
| Sodium | 3,000–5,000 mg/day | Headache, dizziness on standing, tiredness, brain fog | Salt on food, broth, pickles, olives, cheese |
| Potassium | 3,000–4,700 mg/day | Cramps, weakness, irregular heartbeat in severe cases | Avocado, leafy greens, salmon, mushrooms |
| Magnesium | 300–500 mg/day | Muscle cramps, twitches, poor sleep | Pumpkin seeds, almonds, leafy greens, dark chocolate |
These are total daily intakes, food, drinks and added salt combined, in the ranges commonly recommended for keto by low-carb researchers such as Stephen Phinney and Jeff Volek, and used by programmes like Virta. They are deliberately higher for sodium than standard public-health advice, because a person in ketosis genuinely loses more of it. Water and minerals work as a pair: use our water intake calculator to set your fluid target, and the urine colour check on the same page to see whether you are hitting it.
The Safety Part, Please Read This
Higher sodium and potassium intakes are not safe for everyone. If you have kidney disease, heart failure or high blood pressure, or you take medicines that affect potassium, ACE inhibitors, ARBs and potassium-sparing diuretics are common ones, do not follow general keto electrolyte targets, and do not take potassium supplements or potassium-based “lite salt” in quantity, without your doctor’s say-so. Excess potassium with impaired kidneys can be life-threatening. That is why the calculator asks first and refuses to give numbers when the answer is yes. It is also why we say: get potassium mostly from food, and if symptoms like a racing or fluttering heart show up, get checked promptly rather than calculating harder.
Food First, Supplements Second
For most people, the practical routine is simple: salt your food properly, drink a cup of broth or stock on rough days, eat an avocado or a big portion of leafy greens daily, and keep a handful of pumpkin seeds or almonds around. Magnesium is the one many people do end up supplementing, often in the evening, because hitting 400 mg from keto food alone takes planning. And if your problem is constipation rather than cramps, a very common keto complaint, magnesium and fluids are still the first place to look; our Bristol stool checker will help you work out what your stool is telling you. Planning meals around your numbers is easier alongside your keto macro targets.
Keto Electrolyte FAQs
How long does keto flu last?
For most people, a few days once electrolytes and fluids are fixed, it is usually worst around days 2 to 5 and is largely preventable by hitting your sodium target from day one. If symptoms persist beyond the first couple of weeks despite good electrolytes, see a doctor rather than assuming it is still “adaptation”.
Is 5,000 mg of sodium not dangerous?
It is higher than general public-health guidance, and that guidance exists for good reasons for the general population. On keto, sodium losses are measurably higher, which is why low-carb researchers recommend these ranges for healthy adults in ketosis. But “healthy adults” is doing real work in that sentence, anyone with blood pressure, heart or kidney issues should treat this as a conversation with their doctor, not a target.
Can I just take electrolyte drinks or powders?
You can, but read the label: many popular sports and “keto” drinks contain only token amounts, a few hundred milligrams of sodium per serving, and some add sugar or maltodextrin that works against ketosis. Compare the label against your targets above; most people find salted food and broth cover sodium better and more cheaply.
What about electrolytes on longer fasts?
The same minerals matter, and the longer the fast, the more they matter, extended fasts (over 24–48 hours) are where electrolyte mistakes cause real problems. Our fasting timer tracks your schedule, but for multi-day fasts, plan electrolytes deliberately and stop the fast if you feel unwell.