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If you have had a kidney stone, drink 2.5–3 liters of water a day and keep salt under 6 grams

  • High value
  • Evidence A
  • Buys life
  • Free
  • Takes minutes
  • Some willpower

In plain words

For someone who has had a first calcium stone, if they do nothing, about a quarter will get another within five years. Among people who drank enough water every day, only a little over 10% had a recurrence in five years, more than half fewer. The British guideline gives the amount as 2.5 to 3 liters of water a day and no more than 6 grams of salt.

Cost

Free. Make drinking water through the day a habit. On days you sweat a lot, drink more. The hard part is remembering every day.

What you get

A 5-year controlled trial with random assignment to two groups, in 199 patients with a first calcium stone and no identifiable cause (also called idiopathic calcium stones). One group drank at least 2 liters of water a day, and the other did nothing. Recurrence within 5 years was 12/99 (12.1%) in the extra-water group and 27/100 (27.0%) in the no-intervention group, P=0.008. The smaller the P value, the less likely the difference between the two groups is chance. Average time to recurrence: 38.7±13.2 months versus 25.1±16.4 months, P=0.016. In the 24-hour urine volume measured at the start, stone patients were clearly lower than people without stones: for men 1,057±238 mL versus 1,401±562 mL (P<0.0001), and for women 990±230 mL versus 1,239±440 mL (P<0.001). Clause 1.8.1 of the NICE guideline NG118 recommends that adults drink 2.5 to 3 liters of water a day and that children and teenagers drink 1 to 2 liters depending on age. Add a little fresh lemon juice to the water, avoid fizzy drinks, and keep adults' salt to no more than 6 grams a day.

Notes

Recurrence fell by about 55%, and it costs nothing, so under this book's ranking rule this is the best value in the section. What to watch is the 24-hour urine volume, with a target of 2 to 2.5 liters or more, not how much you drink. People who sweat a lot or work in high heat need to drink even more. That trial was in patients with a first idiopathic calcium stone. Stones are not all of one kind, and uric-acid stones, infection stones and cystine stones each have their own measures. People who have had a recurrence are worth a stone analysis and a 24-hour urine test before deciding whether to add medicine. Don't give up calcium to prevent stones; see §6.21. If you get severe cramping pain in your side or abdomen during an attack, go to the hospital; drinking more water will not wash the stone out. Painless blood in the urine has other causes that need checking; see §1.27.

Evidence grade
A : Specific numbers from meta-analyses, large cohorts or randomized trials; for law and policy, the statute or official text.
Sources
  1. Borghi L, Meschi T, Amato F, Briganti A, Novarini A, Giannini A (1996). Urinary volume, water and recurrences in idiopathic calcium nephrolithiasis: a 5-year randomized prospective study. The Journal of Urology, 155(3), 839-843. https://doi.org/10.1016/s0022-5347(01)66321-3
  2. National Institute for Health and Care Excellence (2019). Renal and ureteric stones: assessment and management. NICE guideline NG118，第 1.8.1 条. https://www.nice.org.uk/guidance/ng118/chapter/Recommendations

Mentioned in

Translated from the Chinese original. Original book, section 16, tip 8. This section is about health and medicines. It is general information, not a substitute for a doctor’s diagnosis or prescription. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer