Does tonic water help with leg cramps?

Nobody has tested it. We found no randomized trial, no systematic review and no registered study of tonic water itself for cramps. What has been tested is quinine, the bitter ingredient in tonic, given as a medicine. A Cochrane meta-analysis of 23 trials in 1586 people found that quinine tablets, most often 300 mg a day, cut the number of cramps by 28% over two weeks against placebo, and the reviewers rated that evidence low quality. A liter of tonic water at the US legal limit holds about 83 mg of quinine. That is less than half the lowest dose in those trials.

Unsettled. Tonic water for cramps has never been studied, so there is no result to report either way. The case for it is borrowed from quinine tablets, which show a modest effect on low-quality evidence at doses a glass does not reach. And the US drug regulator says the risks of quinine for night cramps outweigh any benefit.

What the trials found

Quinine tablets, pooled

The Cochrane review pooled trials of quinine at 200 to 500 mg a day in people with muscle cramps of any cause. Against placebo, quinine reduced the number of cramps over two weeks by 28%, cramp intensity by 10% and the number of days with cramps by 20%. The abstract gives these as percentages and does not give the starting number of cramps, so we cannot turn them into cramps a week. The evidence on cramp number and cramp days is low quality and on intensity moderate quality. More than half of the participants, 58%, came from five unpublished studies. The review also says there is no evidence to judge the right dose or how long to take it.

Two small trials with counts

In a crossover trial of 27 men aged 38 to 73 with at least six leg cramps a month, quinine at 500 mg a day, split between supper and bedtime, at least halved the number of cramps in 13 of the 27. The response usually came within 3 days. The trial was small and included only men.

In people on dialysis, 325 mg of quinine at bedtime brought leg cramps from about 11 a month down to 3.6 after a month. Vitamin E brought them to 3.3, a similar effect. That trial ran a placebo only in a short lead-in period, so it compares two treatments with each other rather than with nothing, and its authors suggested trying vitamin E first because of quinine's toxicity.

Tonic water itself

US rules cap quinine in carbonated drinks such as tonic at 83 parts per million, about 83 mg per liter. One laboratory analysis of two commercial tonic waters found 67.9 and 61.3 mg per liter. So a liter of tonic, at the cap, holds less than half the lowest quinine dose tested against cramps. We did not find any trial that tested whether that smaller amount does anything.

Who should be careful

Not for everyone. The FDA-approved label for quinine carries a boxed warning. Using quinine to treat or prevent night leg cramps may cause serious and life-threatening blood reactions, including a low platelet count and a condition that damages the kidneys and small blood vessels, and the label judges that this risk outweighs any benefit for night cramps. That warning is about medicinal doses.

In the Cochrane trials, which lasted up to 60 days, minor side effects were 3% more common on quinine than on placebo, with a confidence interval from 0% to 6%, mostly stomach and gut symptoms. Trials of that size and length are too small to see the rare serious reactions on the label.

Longer use has been looked at in observational data. In a UK primary care cohort of 175,195 people with cramps or restless legs, those who took quinine at 100 mg a day or more for at least a year (median 203 mg a day) died at a rate of 4.2 per 100 person-years, against 3.2 in those who did not, an adjusted hazard ratio of 1.24 (95% CI 1.21 to 1.27). This is observational, so it cannot prove that quinine caused the deaths, and it is about tablets.

Pregnancy: a Cochrane review of treatments for leg cramps in pregnancy, 8 trials with 576 women, left quinine out altogether because of its known adverse effects. Older adults on other medicines: one case report describes a dangerous heart rhythm in a 91-year-old woman who was taking quinine or a related drug in three forms at once, hydroxychloroquine, quinine tablets for leg cramps, and gin with tonic water. The tonic's share in that could not be separated.

We found no data on whether the blood reactions on the quinine label occur at the amounts in tonic water. That is a gap in the evidence, and it is not a statement that tonic is safe for everyone. If you take quinine or a related medicine, or you are pregnant, ask the person treating you before using tonic as a remedy.

What expert bodies say

The American Academy of Neurology, in a 2010 assessment of 24 prospective trials, rated quinine likely effective for muscle cramps. It advised avoiding it for routine use because of its toxicity, and said it may be considered for an individual trial in selected patients once side effects are taken into account. We found no update of that guideline. The FDA position is the boxed warning above. US food law sets the 83 parts per million cap for tonic and says nothing about cramps.

How we searched

What would change this answer

• A randomized trial of tonic water, at the amounts people drink, with cramps as the outcome. None exists and none is registered.
• Trials that find the right dose and length of quinine treatment. The Cochrane review says there is no evidence to judge either.
• Data on the serious blood reactions at the low, repeated intakes that come from drinking tonic regularly.

For quinine in a glass, see the gin and tonic page. For the other common cramp remedy, see our review of magnesium and cramps.

Sources

1. ev-twc-01 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of RCTs · n = 1586
   The most commonly used quinine dosage was 300 mg/day (range 200 to 500 mg). ... Compared to placebo, quinine significantly reduced cramp number over two weeks by 28%, cramp intensity by 10%, and cramp days by 20%.
   
   Who: people of all ages with muscle cramps of any location and cause; quinine 200-500 mg/day, most often 300 mg/day
   Effect: cramp number -28%, cramp intensity -10%, cramp days -20% over two weeks vs placebo; cramp duration not affected
   Certainty: Quinine in tablets, not tonic. 58% of participants are from five unpublished studies.
   Cochrane Database Syst Rev, 2015 · checked 2026-10-07 · we read the abstract
2. ev-twc-02 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of RCTs · n = 1586
   There is low quality evidence that quinine (200 mg to 500 mg daily) significantly reduces cramp number and cramp days and moderate quality evidence that quinine reduces cramp intensity.
   
   Who: RCTs of quinine for muscle cramps, GRADE assessment
   Effect: low-quality evidence for cramp number and cramp days; moderate-quality evidence for intensity
   Certainty: A GRADE quality assessment from the authors' conclusions.
   Cochrane Database Syst Rev, 2015 · checked 2026-10-07 · we read the abstract
3. ev-twc-03 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of RCTs · n = 1586
   A significantly greater number of people suffered minor adverse events on quinine than placebo (risk difference (RD) 3%, 95% confidence interval (CI) 0% to 6%), mainly gastrointestinal symptoms.
   
   Who: people with muscle cramps in RCTs of quinine, use up to 60 days
   Effect: minor adverse events RD 3% (95% CI 0% to 6%); major adverse events RD 0% (95% CI -1% to 2%); thrombocytopenia 0.12%
   Certainty: Duration in the trials up to 60 days; rare severe reactions are not visible in RCTs of this size (see ev-twc-09, ev-twc-11).
   Cochrane Database Syst Rev, 2015 · checked 2026-10-07 · we read the abstract
4. ev-twc-04 · Meta-analysis or systematic review · Cochrane systematic review, stated evidence gap · n = 23 trials
   There is no evidence to judge optimal dosage or duration of quinine treatment.
   
   Who: RCTs of quinine for muscle cramps
   Effect: optimal dose and duration unknown; tonic water untested
   Certainty: The second part of the claim is our empty search (corpus, Europe PMC, CT.gov 2026-10-07), not the words of the review.
   Cochrane Database Syst Rev, 2015 · checked 2026-10-07 · we read the abstract
5. ev-twc-05 · Randomized controlled trial(s) · randomized double-blind placebo-controlled crossover trial · n = 27
   Thirteen of 27 patients had at least a 50% reduction in the number of cramps while receiving quinine; the response was usually seen within 3 days.
   
   Who: male veterans aged 38-73 with at least six leg cramps a month; quinine sulfate 200 mg at supper and 300 mg at bedtime for 4 weeks
   Effect: 13 of 27 had at least 50% fewer cramps on quinine; lower frequency and sleep disturbance vs placebo, severity unchanged
   Certainty: Small n, men only; the 500 mg/day dose is six times more than a liter of tonic at the 83 ppm limit.
   Arch Intern Med, 1992 · checked 2026-10-07 · we read the abstract
6. ev-twc-06 · Randomized controlled trial(s) · randomized double-blind double-dummy trial · n = 29 completers of 40
   The vitamin E and quinine groups had a 1 month reduction in leg cramps to 3.3 and 3.6, respectively (p < 0.0005 for both groups combined); this was sustained at 2 months.
   
   Who: patients on dialysis with a history of leg cramps; quinine 325 mg or vitamin E 400 IU at bedtime for 2 months
   Effect: cramps per month 10.9 to 3.6 on quinine, 10.4 to 3.3 on vitamin E; difference 95% CI -3.8 to +3.2
   Certainty: No parallel placebo group (placebo only in the run-in period); the authors advise vitamin E first because of quinine toxicity.
   ASAIO J, 1992 · checked 2026-10-07 · we read the abstract
7. ev-twc-07 · Position of an expert body · federal food additive regulation
   Not to exceed 83 parts per million, as quinine.
   
   Who: carbonated beverages sold in the United States
   Effect: maximum 83 ppm quinine (about 83 mg/L); a liter at the cap holds less than half the lowest trial dose
   Certainty: Comparison with doses is our arithmetic (ppm ≈ mg/L) against ev-twc-01.
   21 CFR 172.575 Quinine, eCFR, current as of 2026-09-01 · checked 2026-10-07 · we read the section
8. ev-twc-08 · Laboratory or animal data · case report with HPLC analysis · n = 2 products
   Both Schweppes and CANADA DRY brands of tonic water emitted fluorescent light upon ultraviolet A irradiation, and contained quinine at concentrations of 67.9 and 61.3 mg/L, respectively.
   
   Who: two commercial tonic water brands analyzed in a case report
   Effect: quinine 67.9 mg/L (Schweppes) and 61.3 mg/L (Canada Dry)
   Certainty: Two brands, Japan 2013; not a market sample.
   J Dermatol, 2013 · checked 2026-10-07 · we read the abstract
9. ev-twc-09 · Position of an expert body · FDA-approved drug label, boxed warning
   Quinine sulfate capsules use for the treatment or prevention of nocturnal leg cramps may result in serious and life-threatening hematologic reactions, including thrombocytopenia and hemolytic uremic syndrome/thrombotic thrombocytopenic purpura (HUS/TTP).
   
   Who: people taking prescription quinine sulfate for nocturnal leg cramps
   Effect: thrombocytopenia and HUS/TTP; risk judged to outweigh any benefit for nocturnal leg cramps
   Certainty: The label is about medicinal doses; there are no data here on such reactions from the amounts in tonic (only allergic cases).
   Quinine sulfate capsules label (Lupin), DailyMed, set 1f32f05c-a215-40be-b951-e41a7b54a8a0, published 2025-11-17 · checked 2026-10-07 · we read the section
10. ev-twc-10 · Position of an expert body · evidence-based guideline (AAN assessment) · n = 24 trials
    Although likely effective (Level A), quinine derivatives should be avoided for routine use in the management of muscle cramps because of the potential of toxicity, but in select patients they can be considered for an individual therapeutic trial once potential side effects are taken into account.
    
    Who: patients with muscle cramps; review of 24 prospective trials
    Effect: quinine likely effective (Level A) but should be avoided for routine use; individual trial only in selected patients
    Certainty: Guideline from 2010; no update found.
    Neurology, 2010, 74(8):691-6, AAN Therapeutics and Technology Assessment Subcommittee · checked 2026-10-07 · we read the abstract
11. ev-twc-11 · Observational data · retrospective cohort (research letter) · n = 175195
    There were 11 598 deaths (4.2 per 100 person-years) among the 44 699 exposed individuals vs 26 753 (3.2 per 100 person-years) among the 130 496 unexposed individuals (adjusted hazard ratio [HR], 1.24 [95% CI, 1.21-1.27]).
    
    Who: adults with idiopathic muscular cramps or restless leg syndrome, UK primary care 1990-2014; exposed = quinine at least 100 mg/d for at least 1 year (median 203 mg/d)
    Effect: adjusted HR 1.24 (95% CI 1.21-1.27); under 50 years HR 3.06 (2.51-3.73); 300-399 mg/d HR 1.83 (1.72-1.94)
    Certainty: Observational data, possible residual distortion; medicinal doses, not a tonic.
    JAMA, 2017, 317(18):1907-1909 · checked 2026-10-07 · we read the fulltext
12. ev-twc-12 · Meta-analysis or systematic review · Cochrane systematic review · n = 8 studies, 576 women
    Quinine was excluded for its known adverse effects.
    
    Who: RCTs of treatments for leg cramps in pregnant women
    Effect: quinine excluded from review on safety grounds
    Certainty: Position of a review on selection, not its own analysis of quinine harm.
    Cochrane Database Syst Rev, 2020 · checked 2026-10-07 · we read the abstract
13. ev-twc-13 · Laboratory or animal data · case report · n = 1
    Her medical history revealed that she was taking quinine or a derivative in three different forms: hydroxychloroquine, quinine sulfate (for leg cramps), and her gin mixed with tonic water (containing quinine).
    
    Who: one 91-year-old woman taking hydroxychloroquine, quinine sulfate for leg cramps and gin with tonic
    Effect: non-sustained polymorphic ventricular tachycardia with prolonged QT
    Certainty: The contribution of tonic is not separated.
    J Gen Intern Med, 2016 · checked 2026-10-07 · we read the abstract