Gin and tonic: the quinine is real, the cramp cure is not in the glass

In trials, quinine taken as a prescription medicine modestly reduced leg cramps. A Cochrane meta-analysis of 23 trials in 1586 people found that 200 to 500 mg a day, most often 300 mg, cut the number of cramps by 28 percent over two weeks against placebo. Tonic water is a much smaller dose. US rules cap quinine in carbonated drinks at 83 parts per million, so even a full liter at that limit holds about 83 mg, below the lowest dose used in those trials. Two commercial tonics analyzed for a Japanese case report in 2013 held 67.9 and 61.3 mg per liter. We found no trial that tested tonic water itself against cramps. Even for the drug, the Cochrane authors say there is no evidence to judge the best dose or duration. In those trials minor side effects were about 3 percent more common than on placebo. What a gin and tonic reliably delivers is alcohol and sugar. US survey data code one drink as 225 g carrying about 189 calories, 19 g of ethanol and 14.8 g of sugar from regular tonic, recalculated from the 100 g values, and the real strength depends on who pours it.

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• In USDA survey data a gin and tonic made with regular tonic carries 6.57 g of sugars per 3.5 oz (100 g), about 14.8 g in a 225 g drink, all of its carbohydrate. — US dietary survey food coding Evidence E source
  Total sugars 6.57 g/100 g = carbohydrate 6.57 g/100 g; 14.8 g per 225 g drink
• In a case report of a fixed skin eruption traced to tonic water, laboratory analysis found 67.9 and 61.3 mg/L of quinine in two commercial brands. — one 26-year-old man with recurrent fixed eruption; two commercial tonic waters analyzed (n = 1) Evidence D source
  Quinine 67.9 mg/L (Schweppes) and 61.3 mg/L (Canada Dry); eruption confirmed by oral challenge and patch test

What a real portion looks like

• USDA dietary survey data count one gin and tonic as a 225 g drink, with a 1 fl oz measure set at 30 g. — US dietary survey food coding Evidence E source
  1 drink = 225 g; 1 fl oz = 30 g; quantity not specified = 225 g
• USDA survey data put a gin and tonic at 84 calories and 8.5 g of ethanol per 3.5 oz (100 g), about 189 calories and 19 g of alcohol in a 225 g drink. — US dietary survey food coding Evidence E source
  84 calories/100 g, ethanol 8.5 g/100 g; per 225 g drink 189 calories and 19.1 g ethanol

What your body absorbs

• In a randomized crossover trial in 12 adults, the same dose of vodka mixed with a diet cola gave a higher peak breath alcohol (38.3 vs 34.8 ug/100 mL) than with sugared cola, with faster stomach emptying. — 12 healthy volunteers (8 male, 4 female) aged 19-64, vodka 0.5 g/kg with diet or regular coke, single sessions (n = 12) Evidence B source
  Peak BrAC 38.3 +/- 9.45 vs 34.8 +/- 6.82 ug/100 mL; gastric half-emptying 100.09 vs 110.74 min

What it does to your health

• In a randomized trial in 14 men, 50 g of ethanol with 50 g of glucose pushed blood glucose below 50 mg/dL (2.8 mmol/l) in four, with a significantly deeper later fall than ethanol with a starch drink. — 14 men aged 20-50 (9 normal weight, 5 obese), 50 g glucose or maize starch with 50 g ethanol over one hour (n = 14) Evidence B source
  4 of 14 fell below 2.8 mmol/l plasma glucose after glucose plus alcohol; later glucose fall significantly lower than with starch plus alcohol

Safety, limits and interactions

• US federal rules cap quinine in carbonated drinks such as tonic water at 83 parts per million and require the label to declare it. — carbonated beverages sold in the United States Evidence E source
  Maximum 83 ppm quinine (as hydrochloride or sulfate salt); mandatory quinine declaration on label
• A case report describes mouth ulcers and a fixed skin lesion in a 31-year-old man hours after a gin and tonic, with a positive patch test to quinine. — one 31-year-old man (n = 1) Evidence D source
  Lip and oral ulcers plus fixed erythematous lesion within 24 h; patch test quinine ++ and tonic water ++
• The FDA-approved quinine sulfate label warns that quinine may enhance the action of warfarin and other oral anticoagulants. — patients on warfarin or other oral anticoagulants taking quinine sulfate Evidence E source
  Possible potentiation of oral anticoagulants
• The US alcohol institute (NIAAA) lists abnormally low blood sugar as a possible reaction when alcohol, as in a gin and tonic, is mixed with diabetes medicines such as the sulfonylureas glipizide, glyburide and chlorpropamide. — People who drink alcohol while taking common prescription or over-the-counter medicines (n = -) Evidence E source
  Diabetes medicines (sulfonylureas) + alcohol: abnormally low blood sugar, flushing reaction

What people believe that the data does not support

• A Cochrane meta-analysis of 23 trials (1586 people) found medicinal quinine, most often 300 mg a day (range 200 to 500 mg), cut cramp number by 28% over two weeks versus placebo. — people of all ages with muscle cramps of any cause, quinine usually 300 mg/day, up to 60 days (n = 1586) Evidence A source
  Cramp number -28%, cramp intensity -10%, cramp days -20% over two weeks vs placebo; minor adverse events RD 3% (95% CI 0% to 6%)

Who this works differently for

• A case report links dangerous heart rhythm and a prolonged QT interval in a 91-year-old woman to quinine taken in three forms, one of them gin with tonic water. — one 91-year-old woman taking hydroxychloroquine, quinine sulfate for leg cramps and gin with tonic (n = 1) Evidence D source
  Non-sustained polymorphic ventricular tachycardia with prolonged repolarization
• A gin and tonic is an alcoholic drink. CDC defines moderate drinking as two drinks or less in a day for men and one drink or less in a day for women, says people younger than 21 and people who are or might be pregnant should not drink at all, and states that even less than 1 drink per day can raise the risk of certain cancers. — adults of legal drinking age (21 or older), people younger than 21, pregnant people Evidence E source
  Moderate use: 2 drinks or less a day for men, 1 or less for women, under 1 drink a day can raise risk of certain cancers
• CDC states there is no known safe amount of alcohol during pregnancy and that all types of alcohol, including wine, beer and liquor, can be harmful, with fetal alcohol spectrum disorders as the possible lifelong outcome. A gin and tonic contains gin, a liquor, so this applies to it. — pregnant women Evidence E source
  No known safe amount of alcohol in pregnancy, risk of fetal alcohol spectrum disorders

What is still unknown

• The Cochrane review on quinine for cramps states there is no evidence to judge an optimal dose or duration, and no trial in the corpus tested tonic water itself against cramps. — trials of quinine for muscle cramps, 23 RCTs (n = 1586) Evidence A source
  Optimal dose and duration unknown; tonic water untested

The bottom line

The sugar in the mixer does more than add calories. In a randomized trial from 1984, 14 men drank 50 g of ethanol over an hour together with 50 g of glucose, and four of them fell below 50 mg/dL (2.8 mmol/l) of plasma glucose. The same alcohol with a starch drink gave a significantly smaller later fall. That was a glucose solution standing in for a sweet mixer, in men only, with a small sample, and it did not include anyone taking insulin or other glucose-lowering drugs. Slimline tonic removes the sugar, and one trial suggests the alcohol may then arrive faster. In a randomized open-label crossover trial in 12 adults, vodka at 0.5 g per kg of body weight mixed with diet cola gave a higher peak breath alcohol, 38.3 against 34.8 micrograms per 3.4 fl oz (100 mL), than the same vodka with sugared cola. The stomach also emptied faster. The mixer there was cola. We found no such trial with tonic. Who should be careful. Quinine can cause reactions at drink doses in people who are sensitive to it, and the 83 ppm cap is a regulatory limit rather than a safety threshold for them. One case report describes a 31-year-old man with ulcers on the lips and inside the mouth 3 to 4 hours after a gin and tonic and a fixed red skin lesion a day later, with positive patch tests to quinine and to tonic water. Another describes a recurring fixed skin eruption confirmed by an oral challenge with tonic. A 91-year-old woman taking hydroxychloroquine and quinine sulfate for cramps, and drinking gin with tonic, developed a dangerous heart rhythm with prolonged repolarisation, and her doctors could not separate the share of the tonic. The approved quinine sulfate label warns that quinine may enhance the action of warfarin and other oral anticoagulants. That label covers medicinal doses, and nobody knows whether tonic amounts matter. If you take quinine drugs or a blood thinner, count tonic as a source. This page has no card on alcohol in pregnancy, on alcohol taken with insulin or other glucose-lowering drugs, on a safe upper amount of alcohol or on its long-term risks. Those gaps are not reassurance, and the ethanol in the glass is the part they concern.

Sources

1. gnt-r8-03 · dataset
   FNDDS 2710633 Gin and tonic: Total Sugars 6.57 g/100 g, 1 drink 225 g 14.8 g · Carbohydrate, by difference 6.57 g/100 g, 1 drink 14.8 g
   USDA FNDDS 2021-2023 via FoodData Central, food code 93301060 (fdc_id 2710633) · checked 2026-09-29
2. gnt-r8-09 · case report
   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.
   J Dermatol, 2013 · checked 2026-09-29
3. gnt-r8-01 · dataset
   FNDDS 2710633 Gin and tonic (food code 93301060): 1 drink 225 g · 1 fl oz 30 g · Quantity not specified 225 g
   USDA FNDDS 2021-2023 via FoodData Central, food code 93301060 (fdc_id 2710633) · checked 2026-09-29
4. gnt-r8-02 · dataset
   FNDDS 2710633 Gin and tonic: Energy 84 kcal/100 g, 1 drink 225 g 189.0 kcal · Alcohol, ethyl 8.5 g/100 g, 1 drink 19.1 g
   USDA FNDDS 2021-2023 via FoodData Central, food code 93301060 (fdc_id 2710633) · checked 2026-09-29
5. gnt-r8-04 · randomized crossover trial
   Diet coke increased both the peak BrAC (38.3 ± 9.45 vs. 34.8 ± 6.82 μg/100 mL) and the area under the breath ethanol curve between 0 and 180 minutes (45249.0 ± 95.7 vs. 40439.25 ± 72.5 μg·min/L).
   Toxicol Lett, 2025 · checked 2026-09-29
6. gnt-r8-05 · randomized trial
   When 14 men (9 normal weight and 5 obese) aged between 20 and 50 years consumed a 50 g glucose load together with 50 g ethanol over an hour, their early plasma insulin response was significantly higher and their later fall in plasma glucose significantly lower than after drinking the same amount of a starch solution (maize meal) and alcohol. In four subjects (3 of them non-obese) plasma glucose concentrations dropped below 2.8 mmol/l after drinking the glucose-alcohol solution.
   Alcohol Alcohol, 1984 · checked 2026-09-29
7. gnt-r8-08 · regulation
   In carbonated beverages as a flavor. Not to exceed 83 parts per million, as quinine. Label shall bear a prominent declaration of the presence of quinine either by the use of the word “quinine” in the name of the article or through a separate declaration.
   21 CFR 172.575 Quinine, eCFR, current as of 2026-09 · checked 2026-09-29
8. gnt-r8-10 · case report
   A 31-year-old male patient who, after 3-4 hours of consuming "Schweppes®" gin with tonic water, manifested ulcers on the lips and oral cavity, and a fixed erythematous lesion on the second phalanx of the hand, 24 hours later.
   Rev Alerg Mex, 2023 · checked 2026-09-29
9. gnt-r8-12 · drug label
   Cinchona alkaloids, including quinine, may have the potential to depress hepatic enzyme synthesis of vitamin K-dependent coagulation pathway proteins and may enhance the action of warfarin and other oral anticoagulants.
   Quinine sulfate label, DailyMed, set 8cd4d427-50ac-4f9c-a029-e7c2d063679a, effective 2025-10-31 · checked 2026-09-29
10. sf-alcmed-r5-9 · agency advice
    Abnormally low blood sugar levels, flushing reaction (nausea, vomiting, headache, rapid heartbeat, sudden changes in blood pressure); symptoms of nausea and weakness may occur (metformin)
    NIAAA, Harmful Interactions: Mixing Alcohol with Medicines (brochure, revised 2014) · checked 2026-10-08
11. gnt-r8-06 · meta-analysis
    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%.
    Cochrane Database Syst Rev, 2015 · checked 2026-09-29
12. gnt-r8-11 · case report
    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).
    J Gen Intern Med, 2016 · checked 2026-09-29
13. sf-alclim-r1-gintonic-1 · agency advice
    The Dietary Guidelines for Americans recommends that adults of legal drinking age (21 or older) should not drink alcohol or drink in moderation if they choose to drink alcohol...Moderate alcohol use is: For men—two drinks or less in a day. For women—one drink or less in a day...You shouldn't drink at all, even in moderation, if you: Are younger than 21. Are pregnant or might be pregnant...Even low levels of alcohol use (less than 1 drink per day) can raise the risk of certain cancers.
    CDC, About Moderate Alcohol Use · checked 2026-10-08
14. sf-alcpreg-r6-gintonic-1 · agency advice
    There is no known safe amount of alcohol use during pregnancy...All types of alcohol can be harmful, including red or white wine, beer, and liquor...Alcohol use during pregnancy can cause a range of lifelong behavioral, intellectual, and physical disabilities known as fetal alcohol spectrum disorders (FASDs).
    CDC, About Alcohol Use During Pregnancy · checked 2026-10-08
15. gnt-r8-07 · meta-analysis
    There is no evidence to judge optimal dosage or duration of quinine treatment.
    Cochrane Database Syst Rev, 2015 · checked 2026-09-29