Alkaline water side effects: what you actually need to know.

Some people report mild nausea, slight headaches or a change in bowel habits when they first switch from regular tap or purified water to alkaline water. Particularly common when people make a sudden switch rather than a gradual one.

These symptoms typically resolve within a few days to a week as your body adjusts. Similar to what happens with any significant change to diet or hydration routine.

Your stomach produces hydrochloric acid (pH 1.5-3.5) to break down food and kill harmful bacteria. There's a theoretical concern that drinking large amounts of high-pH water with meals could temporarily raise the stomach's pH.

In practice, your stomach is very good at maintaining acidity — it responds to any pH increase by producing more acid. For healthy people drinking normal amounts, this is a non-issue. People with low stomach acid (hypochlorhydria) or atrophic gastritis may want to be more mindful.

Some medications are sensitive to changes in pH or mineral intake. Alkaline water adds calcium, magnesium and potassium — and elevated pH can theoretically affect drug absorption for a small number of medications.

If you take prescription medication — particularly for kidney disease, blood pressure, thyroid conditions, or certain antibiotics — check with your doctor or pharmacist before adding alkaline water as your primary drinking water.

People with chronic kidney disease (CKD) may have difficulty processing minerals or maintaining electrolyte balance. Adding mineralised, alkaline water to a restricted diet without medical guidance could complicate things.

This isn't a risk of alkaline water itself — it's a risk of any change to mineral intake when kidneys aren't functioning normally. The advice is straightforward: talk to your nephrologist before making the switch.

Drinking dramatically more water than your body can process — alkaline or otherwise — can cause a condition called water intoxication. It's rare and usually requires consuming several litres in a very short time.

The advice is the same as for any water: drink to thirst, follow general 2-3L/day guidelines, and don't force-drink large quantities all at once. Spread your intake throughout the day.