Can You Drink Coffee While Fasting?

In 30 seconds

Yes, as long as it’s black. A 12-month fasting trial listed black coffee among the energy-free drinks allowed during the 16-hour fast. Sugar, milk, cream and butter add energy, so they end a strict fast.

• Black coffee fits a zero-calorie fast; additions decide the rest.
• Sugar, syrup, milk, cream and butter add energy, so they end a strict fast.
• Up to 400 mg of caffeine a day is not linked to overt harm in healthy adults; pregnancy has a lower limit.
• Caffeine can shorten sleep; avoid it near bedtime.

Does black coffee break a fast?

No. The fasting trials behind this guide draw the line at energy, not flavour, and plain black coffee sits on the energy-free side. What you add to the cup is what counts.

In a 12-month randomized trial of eating only between noon and 8 p.m., participants could drink water and energy-free drinks such as black tea, coffee and diet sodas (up to two a day) during the 16-hour fast.Source 11

In the 12-week TREAT trial, the time-restricted group was told to eat from 12:00 to 8:00 p.m. and to completely abstain from caloric intake for the rest of the day.Source 22

How much caffeine is too much?

The coffee itself rarely decides whether a fast works. Your caffeine total across the day matters more, especially if extra cups become a way to push through hunger.

A systematic review of 381 studies concluded that up to 400 mg of caffeine a day is generally not associated with overt adverse effects in healthy adults; data for children and adolescents were limited.Source 55

NHS guidance advises no more than 200 mg of caffeine a day during pregnancy and estimates about 100 mg in a cup of instant coffee, noting that filter and coffee-shop coffee can contain more.Source 66

Does coffee count toward your fluids?

Yes. Black coffee adds to your daily fluids, though water is still the simplest main drink during a fast.

NHS guidance says water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count toward your daily fluid intake, and advises drinking caffeine in moderation.Source 1010

For how much to drink in total, see drinking water while fasting.

When should you have your last cup?

Earlier than you might think. If your fast starts in the evening, a late coffee can feel like a helpful bridge, yet it can cut into your night even when you don’t feel wired.

A meta-analysis of 24 studies found that caffeine reduced total sleep time by about 45 minutes on average and estimated that a standard coffee should be consumed at least 8.8 hours before bedtime to avoid that reduction.Source 88

Does caffeine affect insulin while fasting?

Its effect on a fast is unknown. A meta-analysis of seven small randomized trials in healthy people without diabetes found that an acute dose of caffeine lowered insulin sensitivity compared with placebo, but none of these trials tested coffee during a fasting window.Source 77

Who should be careful with coffee?

Frequently asked questions

Tea follows the same logic (tea during intermittent fasting), and milk has its own guide: milk in coffee during a fast.

Talk to a qualified health professional before fasting if you are pregnant or breastfeeding, under 18, living with or recovering from an eating disorder, have diabetes, take insulin or a medicine affected by meal timing, are an older adult, or are acutely ill. Do not change the dose or timing of any medicine without your clinician. See Blimbi’s safety guide.

Related guides

• What Can You Drink While Fasting?

  Water, black coffee and plain tea fit a zero-calorie fast; diet soda adds little or no energy. See what you can drink while fasting and what ends a fast.

• Can You Drink Tea While Fasting? Green, Black and Herbal

  Yes: plain black, green and herbal tea add essentially no energy while fasting. See which additions end the fast and how much caffeine tea adds.

• Does Milk or Creamer in Coffee Break a Fast?

  Yes, on a strict fast: milk, cream and creamers all add energy to coffee. See your options if you want to keep a coffee ritual during a fast.

• Can You Drink Water (and Lemon Water) While Fasting?

  Plain and sparkling water never break a fast, and a long fasting trial encouraged it. See where lemon, juice and coconut water fit and how much to drink.

• Intermittent Fasting for Women: What the Evidence Shows

  Intermittent fasting for women: what small trials found on weight before and after menopause, what's known about hormones and periods, and who shouldn't fast.

Frequently asked questions

Can you drink coffee while fasting?

Yes, if it's black. Plain black coffee is treated as an energy-free drink in fasting research: one 12-month trial allowed coffee, black tea and water during the 16-hour fast. Sugar, milk or cream add energy and end a strict zero-calorie fast.Source 11

Can you drink coffee with milk while fasting?

Not on a strict fast. Milk and cream contain fat, protein and milk sugar, so they add energy, and the trials cited here defined the fast as no caloric intake. Keep coffee black and save the milk for your eating window.Source 33Source 22

How many cups of coffee can you drink while fasting?

For healthy adults, a systematic review found that up to about 400 mg of caffeine a day is generally not linked to overt adverse effects. By NHS estimates that is roughly four cups of instant coffee, or fewer cups of strong filter coffee. In pregnancy the NHS limit is 200 mg a day.Source 55Source 66

Sources

1. 1

   Time-Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population: A Randomized Controlled TrialShuhao Lin et al. American College of Physicians, July 1, 2023.DOI: 10.7326/M23-0052 · PMID: 37364268Human randomized trial

2. 2

   Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical TrialDylan A. Lowe et al. American Medical Association (AMA), November 1, 2020.DOI: 10.1001/jamainternmed.2020.4153 · PMID: 32986097Human randomized trial

3. 3

   Dairy and alternatives in your dietNHS. NHS, December 11, 2023.Official guidance

4. 4

   Use of non-sugar sweeteners: WHO guidelineWorld Health Organization. World Health Organization, May 15, 2023.Official guidance

5. 5

   Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and childrenDaniele Wikoff et al. Elsevier BV, November 1, 2017.DOI: 10.1016/j.fct.2017.04.002 · PMID: 28438661Systematic review and meta-analysis

6. 6

   Foods to avoid in pregnancyNHS. NHS, June 15, 2026.Official guidance

7. 7

   Acute caffeine ingestion reduces insulin sensitivity in healthy subjects: a systematic review and meta-analysisXiuqin Shi et al. Springer Science and Business Media LLC, December 28, 2016.DOI: 10.1186/s12937-016-0220-7 · PMID: 28031026Systematic review and meta-analysis

8. 8

   The effect of caffeine on subsequent sleep: A systematic review and meta-analysisCarissa Gardiner et al. Elsevier BV, June 1, 2023.DOI: 10.1016/j.smrv.2023.101764 · PMID: 36870101Systematic review and meta-analysis

9. 9

   Fasting Safely with DiabetesMartin M. Grajower. National Institute of Diabetes and Digestive and Kidney Diseases, August 26, 2020.Official guidance

10. 10

    Water, drinks and hydrationNHS. NHS, May 17, 2023.Official guidance