Apple cider vinegar is a highly acidic, fermented liquid made from apple juice. It’s a popular cooking ingredient and dietary supplement.

While some people take it straight, others add it to their water, take apple cider vinegar supplements, or drink beverages that contain apple cider vinegar.

Some evidence suggests that the vinegar may help lower blood sugar levels and boost weight loss, both of which are often the goals of many people who fast.

Fasting helps you enter ketosis, a metabolic state in which your body burns stored body fat rather than energy derived from food as its primary fuel source (1).

However, you may wonder whether you can safely take apple cider vinegar while fasting without being kicked out of ketosis. This article reviews how apple cider vinegar affects fasting and how much you should take.

Apple cider vinegar in glass bottle and glass on a wooden board alongside some applesShare on Pinterest
Photography by Aya Brackett

To stay in ketosis in a fasted state, you have to maintain an extremely low carb intake.

This is because carbs are a rapidly available fuel for your body, and if they’re present in high enough quantities, your body will switch back to burning carbs instead of burning stored body fat (1).

One tablespoon of apple cider vinegar contains about 3 calories and less than 1 gram of carbs. Therefore, it’s unlikely that it would affect your fast — unless you took it in large quantities, which can be unsafe (2).

Taking apple cider vinegar while fasting seems to help fight cravings and hunger pangs. Plus, several studies have shown that adding vinegar to a meal helps increase feelings of fullness (3, 4, 5).

Studies have also noted associations between vinegar intake, improved blood sugar levels, and reduced weight (5, 6).

While many of these studies weren’t conducted among fasted people, they suggest that apple cider vinegar may help combat hunger and promote steady blood sugar levels, both of which are useful during a fast.


Apple cider vinegar contains only trace amounts of carbs and is therefore unlikely to negatively affect your fast. Furthermore, it may help you feel more full and maintain your blood sugar levels.

To reap some of the potential benefits of apple cider vinegar, less is more.

Taking 1–2 tablespoons (15–30 mL) daily should be sufficient, as taking too much can lead to some unpleasant side effects like tooth enamel erosion (7).

Alternatively, you can take apple cider vinegar capsules, which contain dehydrated vinegar. With these, it’s best to stick to the recommended serving size on the supplement label.

However, you may want to avoid apple cider gummies and drinks while fasting. There’s no guarantee these products won’t kick you out of ketosis, as they often contain added sugar and calories.


Stick to 1–2 tablespoons (15–30 mL) of apple cider vinegar per day. You can also take apple cider vinegar capsules instead, but gummies and drinks should be avoided while fasting.

Apple cider vinegar should be diluted before consumption.

That’s because vinegar is extremely acidic, and exposure to large amounts of undiluted vinegar can erode your tooth enamel, as well as irritate your esophagus and the lining of your digestive tract (7, 8).

One study in healthy adults noted tooth erosion was present after just 8 weeks of taking 2 tablespoons (30 mL) of vinegar diluted in 1 cup (240 mL) of water twice daily. For this reason, it may be wise to dilute the vinegar even more than this (7).

Try diluting at most 1 tablespoon (15 mL) of vinegar into 8 ounces (240 mL) of water to make it safer to drink. If it’s still too strong for your taste, you can dilute it even further.

If you’d like to protect your teeth even more from the vinegar’s acidity, you can drink the diluted apple cider vinegar with a straw or take it in capsule form.


You should dilute apple cider vinegar before drinking it. It’s very acidic and can damage your tooth enamel and digestive tract. You can dilute 1 tablespoon (15 mL) of apple cider vinegar into 1 cup (240 mL) of water.

Both supplementing with apple cider vinegar and fasting are methods to help control blood sugar levels and promote weight loss, so many people use them in combination.

Some research suggests that apple cider vinegar may help you feel more full, which can be very helpful during a fast.

If you want to add apple cider vinegar to your fasting routine, stick to 1–2 tablespoons (15–30 mL) per day, and make sure to dilute the vinegar in plenty of water.

Overall, a little bit of apple cider vinegar each day might help make your fast more manageable.