Apple Cider Vinegar on an Empty Stomach: What Studies Say

Does it matter if you drink apple cider vinegar on an empty stomach? We found no study comparing fasted with fed, so here is what the timing-related studies did measure, plus one measured glass.

Apple cider vinegar on an empty stomach is not shown to burn fat by any source we read. The drink here is 1 tbsp (15 mL) in 1 cup (237 mL) of water, and we found no study comparing fasted with fed.

Here's the shortcut: the viral claim says first thing in the morning works better, and we found no study that measured that. Nothing on this page comes from tasting the drink. It's published studies, health-site guidance and our labeled arithmetic. For the daily amount, see how much apple cider vinegar per day.

Does an empty stomach change anything?

We found no head-to-head comparison. Harvard Health Publishing says it's unclear when to drink apple cider vinegar and the best time is unknown. It doesn't address the empty stomach. Most recommendations it saw are on the order of 1 to 2 teaspoons before or with meals.

Healthline's dosage page skips the morning too. It says to take vinegar right before a high-carb meal for the blood-sugar use, with no significant effect before a low-carb or high-fiber meal, and that there's no evidence for a pre-meal dose for digestion. It adds that vinegar may cause stomach upset in some people.

The two pages we opened from sellers don't settle it either. BUBS Naturals, which sells apple cider vinegar gummies, says nausea is possible fasted and suggests taking it just before eating, but cites no study for that. Goyval Vinagres, a vinegar producer, gives no quantity at all.

The Food Science / Lab Kitchen Note

The acid is acetic acid. The USDA record for cider vinegar (FoodData Central 173469) notes about 5 percent. Brands vary, so every percent here assumes that 5.

The arithmetic is ours. USDA lists 1 tbsp as 14.9 g, so at 5 percent that's about 0.75 g of acetic acid. Stir it into 1 cup of water and the glass is about 252 mL. Counting water as 1 g per mL, 0.75 g in about 252 g is about 0.3 percent. The full unit conversion lives on the apple cider vinegar and water ratio page.

That's a concentration, not a pH. We found no sourced pH for a diluted glass. Dilution cuts the acid load, but it doesn't turn the drink into water.

Fasted, before a meal or with a meal: what the data show

This compares what published sources timed. It isn't a taste comparison, and we found no study that ran these three side by side. "No sourced data" means we found nothing. The first row is the closest data to fasting; it has no comparison with a dose taken at a meal.

The table is a map of the data, not a ranking. The studies used different people, different vinegars and different outcomes.

What the studies actually found

Two small trials on stomach emptying. Hlebowicz and colleagues, BMC Gastroenterology 2007, was a pilot crossover trial in 10 people with type 1 diabetes and gastroparesis (mean age 67.9). Median gastric emptying rate was 27 percent with water and 17 percent with vinegar. The authors list their limits: small, not randomized, fixed order, no blinding, and postprandial glucose wasn't measured. The 2008 trial in Nutrition Journal was blinded, with 13 healthy adults (mean age 25) eating wheat bread dipped in white wine vinegar, not apple cider vinegar. It found no significant difference in gastric emptying or glucose. Two small groups, two different vinegars, no fasted arm.

Glucose, appetite and nausea. Johnston and colleagues (Annals of Nutrition and Metabolism, 2010) reported four randomized crossover trials of 9 to 10 adults each. Two teaspoons (about 10 g) of vinegar lowered post-meal glucose by about 20 percent versus placebo after a complex-carbohydrate meal, strongest taken with the meal rather than 5 hours before. We only read the abstract, and it tested glucose, not nausea or comfort, with no empty-stomach arm. Darzi and colleagues (International Journal of Obesity, 2014) ran two randomized crossover studies in healthy young normal-weight adults. Lower appetite came with higher nausea ratings, and tasting without swallowing did nothing. We read only the abstract, which doesn't give the sample size. The authors say the effect is largely due to poor tolerability. A 2022 review abstract of 13 studies found short-term appetite suppression with a solid-food meal and none in the long-term trials of 4 to 12 weeks.

Common mistakes

Taking it as a shot. Healthline describes case reports of throat burns after large volumes over long periods. Water goes in the glass first.

Sipping it slowly, straight. Harvard says to dilute because sipping it straight can damage tooth enamel. For the straw, rinse and wait steps, see does apple cider vinegar damage teeth.

Pushing through nausea. Cleveland Clinic lists nausea as a side effect and says if it makes you feel sick, stop. It suggests a few drops in water and working up, to no more than two tablespoons a day.

Substitutions and swaps

Storage

Mix one glass and drink it. None of the pages we read say whether a mixed glass keeps, so we give no duration and there's nothing to reheat.

Nutrition note

The values on the card are estimates, calculated from typical USDA FoodData Central values for cider vinegar, record 173469. Per 100 g it lists 21 kcal, 5 mg sodium, 0.93 g carbohydrate and 0.40 g sugars. One tablespoon is 14.9 g, so about 3 kcal, 0.1 g carbohydrate, 0.1 g sugars and 0.7 mg of sodium. Fiber and saturated fat are entered as 0 per that record, our calculation. Protein and fat are 0. Plain water is counted as adding nothing.

The FDA sets the sodium Daily Value at 2,300 mg, so 0.7 mg is about 0.03 percent of it (our calculation).

Serving tip: water first, level spoon, straw.