Apple Cider Vinegar

What it is

Apple cider vinegar is a naturally fermented beverage made from apples [1]. Its main component is acetic acid [2]. Trial participants mixed it into water or took it as capsules [3] [4].

How it might work

Proposed, and not yet tested directly: vinegar may slow the digestion of starchy carbohydrates, so sugar reaches the blood more slowly. In one study it did not lower the blood sugar rise after plain sugar, and a salt of acetic acid had no effect, which points to digestion of carbohydrates as the route [5]. Another proposed route is slower stomach emptying [3], and a further one is higher glucose uptake by muscle after a meal [6].

What the research says

The strongest evidence concerns blood sugar in type 2 diabetes. A 2025 review of seven controlled trials with 463 people found fasting blood sugar about 21.9 mg/dL lower with apple cider vinegar than with control [7]. Two other reviews found similar falls, about 21 mg/dL [8] and about 8 mg/dL in a mixed group of adults [9]. A 2020 review of six small trials in type 2 diabetes also reported better fasting blood sugar and HbA1c [10], and an 8-week trial of 70 people with type 2 diabetes and dyslipidemia (abnormal blood fats) found fasting blood sugar fell by about 10 mg/dL within the vinegar group, and the fall was larger than in the control group [11].

HbA1c, a three-month average of blood sugar, also fell. The same 2025 review pooled four trials, with 319 people, and found HbA1c 1.53 lower, but the results varied widely and the reviewers rated the pooled result as low certainty [7]. Vinegar also lowered blood sugar after meals. A 2017 review of vinegar trials found the blood sugar rise after a meal was smaller, and the insulin rise was smaller still [12]. Four small crossover trials of 9 to 10 people each found about 20% less blood sugar rise after a meal of complex carbohydrates with about two teaspoons of vinegar [5]. In 16 people with type 2 diabetes, the blood sugar rise was 181 against 311 mmol per minute per litre when vinegar was added to a high-GI meal, and it made no difference with a low-GI meal [13]. In 12 healthy people, the highest of three vinegar doses taken with bread lowered the glucose rise at 30 and 45 minutes and the insulin rise at 15 and 30 minutes [14]. The benefit after a meal depends on the meal, and one review rated the acute vinegar result very uncertain [15].

For body weight, a 2025 meta-analysis of ten randomised trials with 789 adults found a small fall in body weight with apple cider vinegar over 4 to 12 weeks (standardised difference -0.39, 95% CI -0.63 to -0.15), along with falls in BMI and waist size [1]. The effect held when high-risk-of-bias trials were removed, but five of the ten trials had high risk of bias in blinding and the funnel plots suggest possible small-study bias, so the result is uncertain [1]. One of the ten trials reported about 7 kg of weight loss in 12 weeks [16]; independent reviewers described its data as improbable and its effects as extreme compared with earlier vinegar research [16], while the trial's authors replied that their methods were appropriate [17]. Two other reviews found no significant change in BMI: a 25-trial review of 1,320 adults [8], and a 16-study review of 910 people taking 750 to 3,600 mg of acetic acid daily for about 8 weeks, which also found no change in body fat [18]. A 12-week trial of obese Japanese adults found lower body weight, BMI and waist size with 15 or 30 mL of vinegar daily than with placebo [2].

Total cholesterol fell about 6 mg/dL in two reviews [9] [8]. LDL and HDL cholesterol did not change in either. Triglycerides fell in the obese Japanese trial [2] and in a diabetes subgroup of one review [8].

Vinegar may also help people feel full. In 12 healthy adults, the highest vinegar dose with bread raised fullness scores at 30, 90 and 120 minutes [14]. In 27 people, a meal with cinnamon and acetic acid raised fullness at 15 and 30 minutes, but not over two hours [19]. In a trial of 11 healthy people, vinegar or peanut products with a high-GI meal were followed by about 200 to 275 fewer kilocalories later that day, but this was not statistically significant [20].

Insulin resistance results are mixed. Pooled trials found no significant change in HOMA-IR [7] [9] [8]. In a 12-week trial of 94 women with polycystic ovary syndrome taking metformin, apple cider vinegar capsules improved insulin resistance more than placebo did [4].

The main risks are tooth enamel erosion, slower stomach emptying and digestive side effects, described under safety below.

Doses used in studies

Doses were typically 10 to 30 mL (about two teaspoons to two tablespoons) a day, taken for 4 to 12 weeks. Reviews found greater fasting blood sugar effects above 10 mL a day [7]. Weight trials used 15 or 30 mL a day for 12 weeks [2], and the weight review's subgroup at 30 mL a day showed significant effects [1]. A PCOS trial used 1,500 mg of capsules a day for 12 weeks [4]. A meal study used about 10 g, which is two teaspoons, with a meal [5]. These are study doses, not recommendations.

Safety and interactions

Common side effects: in a 12-week trial of 27 adults with type 2 diabetes, 50 to 56% of people taking vinegar drinks or pickles reported at least one side effect by week 6, against 11% of people taking vinegar pills. The difference was not statistically significant. Reported effects included burping, flatulence, acid reflux and bowel changes [21]. A 2020 safety review found the risk seems small at the amounts recommended, but judged the evidence inadequate [22]. Acetic acid supplements, which include vinegar-style products, were described as well tolerated in a 2021 review of 16 studies [18].

Tooth enamel: a 15-year-old girl who drank a glass of apple cider vinegar every day developed erosive tooth wear [23]. In lab tests on extracted teeth, vinegar and apple cider vinegar caused the most demineralisation of nine acidic drinks and preservatives [24].

Stomach emptying: in 10 people with type 1 diabetes and diabetic gastroparesis, median gastric emptying fell from 27% to 17% after 30 mL a day for two weeks. The authors said this could hurt blood sugar control [3].

Skin: a case report describes a chemical burn from applying apple cider vinegar to the skin [25].

Liver and urine: in the 12-week trial of 27 adults with type 2 diabetes, one liver enzyme showed a trend upward with vinegar (p=0.090), and urinary pH fell at week 12. The authors said chronic use may affect liver function [21].

Upper limit: no toxic dose was reported in the studies read. The highest intake in the trials cited here was 2,800 mg of acetic acid a day [21]. Medicines: vinegar lowered blood sugar in the trials [7], so it could add to the effect of diabetes medicines. None of the trials cited was designed to test interactions with insulin or diuretics, and the search did not find a trial measuring potassium levels with apple cider vinegar.

Pregnancy and breastfeeding: the searches did not find trials of apple cider vinegar in pregnant or breastfeeding women. People with gastroparesis showed slower stomach emptying with vinegar [3]. The searches did not find trials in people with kidney disease, liver disease or bleeding disorders.

Caveats and open questions

Most trials are short, 4 to 12 weeks, and small. Trials in the weight review had 17 to 65 people per group, and five of ten had high risk of bias in blinding, with funnel plots suggesting possible small-study bias [1]. Reviews disagree on some outcomes: one 25-trial review found no change in BMI or HOMA-IR [8], and another found fasting blood sugar rose in healthy people who took it [9]. Several trials used vinegar in general rather than apple cider vinegar specifically [5]. The trials measured blood markers such as blood sugar and cholesterol, not heart attacks, strokes or deaths [8]. Long-term effects on blood sugar control and heart health are not known from these studies. One trial in the weight review reported about 7 kg of weight loss in 12 weeks, which independent reviewers called improbable and out of line with earlier vinegar research; the authors disputed that reading [16] [17]. The weight review could not assess body fat, because only one trial reported it [1].