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Medical & Clinical Research Journal — Peer-reviewed health analysis, supplement safety reviews, and clinical research summaries.

Best Time to Drink Apple Cider Vinegar: What Research Shows

By MedClinRes.org Clinical Research Team. Sources checked October 3, 2026. This is an educational summary prepared by the MedClinRes.org team and has not been reviewed by a named clinician. See our Editorial Standards.

Short Answer: Does the Time of Day Matter?

None of the trials we reviewed shows that the time of day changes weight or blood sugar results from apple cider vinegar (ACV). As far as their abstracts show, none randomly assigned people to different times of day and compared them. Mayo Clinic's review of the research concludes that ACV is not likely to cause weight loss and that existing studies are small or limited in other ways. WebMD says there is not much research into the best time to take it, and Healthline says studies of bedtime use are lacking.

Where studies reported a schedule, most tied the vinegar to meals, usually lunch and dinner. The bedtime evidence we found is one very small blood sugar study that showed no significant change overall.

Our earlier article on apple cider vinegar for weight loss recipes mentions morning, pre-meal and bedtime options. This guide looks at what trials actually measured for each timing.

What Each Trial Tested: Dose, Timing and Outcome

Each study is listed with the same details so you can compare them. “Does not show” is our plain-language reading of the limits.

Khezri and colleagues, 2018 (weight and blood fats)

  • Who: 39 people with overweight or obesity.
  • Dose and timing: 30 mL a day, split into 15 mL with salad at lunch and 15 mL at dinner. The sources we reviewed do not describe water dilution.
  • Duration: 12 weeks. Both groups followed a diet with a 250 kcal per day deficit. The comparison group had the diet only, with no placebo.
  • Measured outcome: The ACV group had larger reductions in body weight, BMI, hip circumference and a visceral fat index, plus changes in blood fats. One evidence summary reports about 1.7 kg more weight loss than diet alone; other reports give different figures, so treat that number as approximate.
  • What it shows: In a small group on a calorie-restricted diet, vinegar with lunch and dinner was linked to somewhat more weight loss.
  • What it does not show: It did not compare meal timing with other times. WebMD notes the study was small, short and not blinded, and did not track what participants ate or how much they exercised.

Kondo and colleagues, 2009 (body weight and fat)

  • Who: Adults in Japan with obesity (BMI 25 to 30 by Japanese criteria), in a double-blind trial. Reports differ on the exact number of participants.
  • Dose and timing: A 500 mL drink daily containing 0, 15 or 30 mL of vinegar. Timing relative to meals is not stated in the abstract.
  • Duration: 12 weeks.
  • Measured outcome: Body weight, BMI, visceral fat area, waist size and triglycerides were lower in both vinegar groups than in the placebo group.
  • What it shows: Daily vinegar in a diluted drink was linked to modest changes in this group.
  • What it does not show: It does not say when to drink it. The first author is affiliated with a vinegar manufacturer.

Johnston and colleagues, 2013 (fasting glucose)

  • Who: 14 adults at risk for type 2 diabetes.
  • Dose and timing: A vinegar drink providing 750 mg of acetic acid, twice daily at mealtime, compared with a control pill.
  • Duration: 12 weeks.
  • Measured outcome: Fasting glucose fell more in the vinegar group, at borderline statistical significance (p = 0.05). Two-hour after-meal glucose, insulin and HbA1c did not differ between groups.
  • What it shows: A possible small effect on fasting glucose with mealtime vinegar.
  • What it does not show: With only 14 people, it cannot establish benefit, and it did not test any other time of day.

Johnston, Kim and Buller, 2004 (single-meal insulin response)

  • Who: Adults who were insulin resistant (11) or had type 2 diabetes (10), in a crossover design.
  • Dose and timing: After fasting, 20 g of ACV mixed with 40 g of water and saccharine, taken about two minutes before a high-carbohydrate meal.
  • Duration: One test meal, with measurements over 60 minutes.
  • Measured outcome: Estimated insulin sensitivity after the meal rose 34 percent in the insulin-resistant group (statistically significant) and 19 percent in the type 2 diabetes group (not statistically significant).
  • What it shows: Vinegar right before a carbohydrate-heavy meal may change that meal's blood sugar response in some people.
  • What it does not show: It says nothing about weight loss or long-term glucose control.

White and Johnston, 2007 (bedtime and morning glucose)

  • Who: A small group of adults with type 2 diabetes, in a crossover design. We reviewed the conference abstract; the short report is cited below.
  • Dose and timing: 2 tablespoons of vinegar or water at bedtime with a small snack.
  • Duration: Two days per condition.
  • Measured outcome: Morning fasting glucose did not change significantly overall (about 4 percent lower, not significant). In the six participants who woke with high glucose (above 130 mg/dL on average before the study), vinegar lowered it about 6 percent, or 8 mg/dL.
  • What it shows: A possible effect in a small subgroup.
  • What it does not show: Healthline concludes that bedtime vinegar does not appear to offer more benefit than other times, and that studies on bedtime use are lacking.

A Retracted Trial You May Still See Cited

A 2024 trial in Lebanese adolescents and young adults claimed large weight loss from 5, 10 or 15 mL of ACV daily. The journal's publisher retracted it on September 23, 2025. The retraction notice cites concerns about the statistical analysis, implausible values, the reliability of the dataset, inadequate reporting, and no prospective trial registration. We left it out of the comparison above. Articles that still quote its 6 to 8 kg figures are relying on results the journal no longer stands behind.

Time of Day and Side Effects

Timing matters more for comfort than for results. Vinegar is acidic. Healthline notes it can cause indigestion or reflux in some people, especially before lying down, and suggests allowing 2 to 3 hours before bed. WebMD suggests avoiding it within an hour of bedtime if you are prone to heartburn, and avoiding it on an empty stomach, which can cause nausea. The two sources give different cutoffs, and no official standard exists.

Mayo Clinic notes that frequent drinking can irritate the throat and wear down tooth enamel, and that adding ACV to food may cause fewer side effects than drinking it. Healthline suggests diluting it in water and rinsing your mouth afterward. WebMD suggests using a straw.

Who Should Talk to a Professional First

  • People taking insulin or diabetes medicine. Vinegar can affect blood sugar, and Mayo Clinic notes it may interact with insulin.
  • People taking diuretics. Mayo Clinic says interactions with diuretics and some supplements can lower potassium. WebMD also lists diuretics among medicines that can interact.
  • People with low potassium or kidney disease. WebMD advises caution with both.
  • People with reflux or frequent heartburn. The sources differ on whether vinegar helps or worsens symptoms, so ask your doctor.

Ask your doctor or pharmacist before changing your routine. WebMD notes that supplement forms such as pills, powders and gummies have been studied even less.

What You Can Do Next

  1. If you want to try ACV, note that the trials above that reported a schedule mostly paired a small amount of vinegar with meals, in food or diluted, rather than testing a particular hour of the day.
  2. Stay within the amounts studied. Mayo Clinic notes some studies suggest up to 2 tablespoons a day is acceptable, and that people have used it safely for up to 12 weeks.
  3. Put the bigger effort where the evidence is stronger. Mayo Clinic's weight guidance centers on a balanced diet, burning more calories than you take in, and regular physical activity.
  4. Bring this article to your next appointment if you have questions about how ACV fits with your medicines or conditions.

Sources

  1. Mayo Clinic Staff. Apple cider vinegar for weight loss (page dated March 4, 2025).
  2. Healthline. Should You Drink Apple Cider Vinegar Before Bed? (updated March 27, 2024).
  3. WebMD. Apple Cider Vinegar: Benefits, Uses, Risks, and Dosage (medically reviewed July 11, 2024).
  4. Khezri SS et al. Journal of Functional Foods, 2018;43:95-102. Abstract. Dosing split and additional weight loss figure: Evidence-Based Practice summary.
  5. Kondo T et al. Bioscience, Biotechnology, and Biochemistry, 2009;73(8):1837-43. PubMed.
  6. Johnston CS et al. Journal of Functional Foods, 2013;5(4):2007-2011. Abstract.
  7. Johnston CS, Kim CM, Buller AJ. Diabetes Care, 2004;27(1):281-282. Journal page.
  8. White AM, Johnston CS. Conference abstract, The FASEB Journal, 2007: Vinegar ingestion at bedtime appears to moderate waking hyperglycemia in adults with type 2 diabetes. Short report: Diabetes Care, 2007;30(11):2814-5, PubMed.
  9. Retraction notice, BMJ Nutrition, Prevention & Health, September 23, 2025: PMC record.

This article is for general information and does not replace advice from a qualified healthcare professional.