Water, salt and electrolytes during a fast

The straightforward part: what you can drink

During the fasting portion of a normal daily eating window — 12, 14 or 16 hours, say — plain water is the mainstay, and there's no reason to avoid it or ration it. Plain tea (black, green or herbal without added milk or sugar) and black coffee are also generally considered acceptable during a fast by most fasting guidance, since they contain negligible calories and don't meaningfully break the metabolic state a fast is meant to create. If you take milk or sugar in either, that's a genuine calorie intake and technically breaks the fast, which is worth knowing even if it doesn't much matter for a gentle daily practice.

This is really the whole of the straightforward advice: drink water when thirsty, have tea or black coffee if you enjoy them, and don't overthink the rest. Where it gets more interesting — and where most guidance is either silent or overcomplicated — is what happens with salt and minerals.

Why plain water alone, in large amounts, can leave you feeling worse

It's a genuine and fairly common experience: someone increases their plain water intake substantially during a fast, expecting to feel better, and instead feels light-headed, headachy, or oddly worse rather than refreshed. This happens because water intake and salt balance work together in the body; a large volume of plain water without any accompanying salt can, in some people, particularly when combined with reduced food intake (and therefore reduced dietary sodium) from fasting, contribute to a feeling of low energy, mild nausea or headache that gets mistaken for dehydration and "solved" with yet more plain water, compounding the issue.

The fix is not complicated and doesn't require a supplement: a pinch of salt in a glass of water, or simply not over-drinking beyond ordinary thirst, addresses this for most people. This is a case where "more water is always better" is actually poor advice, and it's worth saying so directly rather than letting the common wisdom go unchallenged.

Where your sodium, potassium and magnesium actually come from

For a normal daily fasting window, there's no need for specialist electrolyte tablets, powders or branded drinks. Sodium, potassium and magnesium mostly come from ordinary food, and getting them within the eating window — through vegetables, legumes, fruit, nuts, seeds, and normally salted cooking — is entirely sufficient for most people doing a 12:12 to 16:8 pattern. Bananas, leafy greens, potatoes, legumes and yoghurt are all reasonably good potassium sources; nuts, seeds and whole grains contribute magnesium; ordinary table salt used in cooking covers sodium.

Where electrolyte supplementation becomes a more genuine consideration is with much longer fasts (multi-day, for instance) or in hot climates with heavy sweating, and even then it's a conversation worth having with a doctor rather than a default purchase, particularly for anyone on blood-pressure medication, where extra sodium intake needs individual thought. For the ordinary daily windows discussed across this site, food within the window does the job. See the sattvic and pranic food guide for more on building meals that are genuinely nourishing rather than just calorie-adequate.

A firm word on dry fasting

Dry fasting — abstaining from water as well as food — turns up periodically in fasting culture, sometimes framed as a more intense or purifying version of intermittent fasting. We do not recommend it, and we want to be direct about why. Water is not a discretionary intake the way food during a fasting window is; the body's tolerance for going without it is measured in hours to at most a few days even in ideal conditions, and dehydration brings risks — to kidney function, to blood pressure regulation, to basic cognitive function and coordination — well before those risks are outweighed by any claimed benefit, and no claimed benefit of dry fasting is established by solid evidence in any case. There is no dry-fasting protocol that we consider appropriate to recommend on this site, for a day, a portion of a day, or any longer period. If you come across dry fasting suggested elsewhere as part of a yoga or spiritual practice, treat it with real caution and do not take it as guidance to follow.

For general guidance on hydration and its place in a daily rhythm outside of fasting specifically, see water and dinacharya.

Simple signals to watch for

Ordinary thirst, a dry mouth or mild fatigue are your cues to drink water, not signs to push through as some kind of test. A headache that develops during a fasting window, especially alongside reduced food intake, is often addressed by a small amount of salt with water, or simply by breaking the fast a little earlier that day and eating properly. Dizziness on standing, marked confusion or a fast, irregular heartbeat are not things to wait out — stop, drink, eat, and if symptoms don't resolve quickly or recur, get medical advice. These same signals are covered from the other direction — knowing when a fast isn't appropriate at all — in when not to fast.