Apple cider vinegar on a wood board with apples

Does Apple Cider Vinegar Break a Fast? Not If You Do This

Forget the mid-morning IF slump.

30-Second Takeaway

  • One to two tablespoons of apple cider won’t break a fast, and might reduce hunger and improve your glucose response. 
  • Because ACV is highly acidic, always dilute it with at least one cup of water and drink it with a straw to reduce damage to your teeth or gut lining. 
  • If you can’t stomach plain diluted ACV, try making your own ACV tonic with lemon, cayenne, ginger, turmeric, and/or monk fruit which won’t break a fast.
  • ACV capsules or gummies are also an option, just watch out for added sugar which will break a fast. 

While intermittent fasting may be worth it for the benefits—including but not limited to fat loss, less inflammation and cravings, and a reduced risk of chronic disease—the short-term downsides like fatigue and hunger make it difficult to stick with (1, 2). One potential solution: Apple cider vinegar.

Studies suggest that apple cider vinegar (ACV) may help reduce hunger which might help you get through your fasting window (3). ACV may also reduce blood sugar levels (including glucose spikes after eating) and boost weight loss—common goals of fasting (4, 5, 6).

But does apple cider vinegar break a fast, will it kick you out of ketosis, and is it safe to take on an empty stomach?

About the Expert:

Imashi Fernando, MS, RD, CDCES is a registered dietitian who works in a large hospital system as a clinical dietitian and provides one-on-one nutrition counseling through her virtual private practice, Brown Sugar Nutrition PLLC.

Does Apple Cider Vinegar Break a Fast?

Nope. “Apple cider vinegar won’t break a fast,” says registered dietitian Imashi Fernando, MS, RD, CDCES. One to two tablespoons of ACV has been shown to be effective and safe for daily consumption, and one tablespoon only has about three calories and less than a gram of carbs (4, 7).

Technically both calories and carbs can break a fast. “Calories from protein, fat, or carbs provide cells with nutrients, which interrupts autophagy (the cellular cleanup process linked to longevity and reduced disease risk),” explains Fernando. While eating a decent amount of carbs kicks you out of ketosis—your body’s main metabolic state during a fast.

But the amount of calories and carbs matters. Three to six calories from one to two tablespoons of ACV is pretty negligible. “Less than half a gram of carbs is not significant enough to disrupt ketosis either,” says Fernando. “Even if you take the upper recommended dose of two tablespoons it’s unlikely to affect your fast.” 

Does Apple Cider Vinegar Take You Out of Ketosis?

No. Apple cider vinegar won’t kick you out of ketosis—the state where your body burns fat for energy rather than carbs. To stay in ketosis, you have to maintain an extremely low carb intake (8). “At only 0.5 grams of carbs per tablespoon, in normal quantities (one to two tablespoons) ACV won’t impact ketosis,” says Fernando.

Benefits of Drinking Apple Cider Vinegar

It may help suppress appetite

Taking apple cider vinegar while fasting seems to help fight cravings and hunger pangs. A handful of short-term studies suggest that ACV may help increase feelings of fullness and suppress appetite (3, 9).

Experts are still working to figure out exactly how it works. Some research suggests apple cider vinegar may delay gastric emptying, helping you feel fuller for longer (10). However, the strong taste of ACV may cause nausea that reduces appetite, rather than directly affecting feelings of fullness (9).

It may improve blood glucose response

“Taking apple cider vinegar before a meal may improve your blood glucose response,” says Fernando. A recent clinical trial found that taking a small dose (<2 tbsp) of ACV before a meal improved insulin resistance and fasting blood sugar among people with diabetes (5). Another found that taking vinegar with bread reduced the blood sugar response for up to 45 minutes afterwards in comparison to eating bread alone (11).

According to Fernando, the positive impact on glucose response is due to delayed gastric emptying, which reduces the rate that glucose is absorbed into the bloodstream and  blood glucose spikes (12). Experts suspect acetic acid, the primary active ingredient in ACV, is responsible for the delayed gastric emptying effect. “Acetic acid is also thought to reduce the breakdown of starch into glucose and positively change the way the body metabolizes carbohydrates,” says Fernando.

Potential Downsides of Drinking Apple Cider Vinegar

It may trigger nausea

While apple cider vinegar may suppress appetite, one study suggests that these effects were largely due to feelings of nausea from the strong taste of ACV (9). “Since ACV doesn’t always sit well, start with a lower dose of ACV (1 tablespoon or less) and increase as tolerated to no more than 2 tablespoons daily,” says Fernando.

Apple cider vinegar gummies or capsules seem like a solid bet if you can’t stomach drinking a cup of diluted ACV. However, according to a recent review they may not provide the same effects as liquid ACV, and might be unsafe (13). You’ll also want to look out for added sugars in the gummies, which will break a fast. ACV tonics are another option, but again the sugar and calories are worth keeping an eye on if you’re fasting.

It can damage your gut lining

Apple cider vinegar is highly acidic. For example, stomach acid has a pH of 1.5 to 2, ACV has a pH of 2 to 3 (compared to water, which has a pH of 7) (14). Regularly drinking it undiluted in high amounts can damage your throat, stomach, and upper GI tract (15). A healthy gut is key for regular digestion, absorption of essential vitamins, minerals, and nutrients, and overall health (16).

“Because of apple cider vinegar’s high acidity, it’s important to dilute ACV with at least 1 cup of water, if not more,” says Fernando. She recommends making your own ACV tonic at home with other ingredients like lemon, ginger, turmeric, or cayenne to take away some of the bite. “Add monk fruit if you like it sweet as this will not break a fast,” she adds.

It can erode tooth enamel

“Daily apple cider vinegar consumption may lead to erosion of the tooth enamel, thanks to the high acidity (17),” says Fernando. Tooth erosion can lead to a host of dental issues including tooth sensitivity, discoloration, and increased risk of cavities (18).

“To reduce the risk of eroding tooth enamel, drink ACV with a straw,” says Fernando. If you want to be extra safe, brush your teeth, use mouthwash, or swish water to avoid any residue sitting on your teeth.

It may interfere with medications

Apple cider vinegar consumption can interact with medications such as digoxin, diuretics, insulin, and other anti-diabetic drugs like Metformin (19). “ACV may reduce potassium levels. Low potassium can increase the side effects of digoxin, while both insulin and diuretics reduce potassium—so when combined with ACV may lead to dangerously low potassium levels which can be life threatening,” says Fernando. Plus, given that ACV may reduce blood sugar levels, taking it alongside diabetes medications may lower blood sugar too much.

Check with your doctor prior to taking apple cider vinegar, especially on an empty stomach.

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12. Hinshaw, L. et al. (2014). Effect of Delayed Gastric Emptying on Postprandial Glucose Kinetics, Insulin Sensitivity, and β-cell function.
13. Feise, N. et al. (2020). Commercial Vinegar Tablets Do Not Display the Same Physiological Benefits for Managing Postprandial Glucose Concentrations as Liquid Vinegar. 
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17. Anderson, S. et al. (2021). Evidence That Daily Vinegar Ingestion May Contribute to Erosive Tooth Wear in Adults.
18. National Institute of Dental and Craniofacial Research (2022). The Tooth Decay Process: How to Reverse It and Avoid a Cavity.
19. Medline Plus (2023). Apple Cider Vinegar.