Does Melatonin Break a Fast? What You Need to Know

January 10, 2026 •

4 min read

Over 3 million people in the US use melatonin supplements to help with sleep. Many of these individuals also practice intermittent fasting and wonder: does melatonin break a fast? The simple answer depends heavily on the supplement's form and your fasting goals.

Quick Summary

Melatonin pills or capsules typically do not break a fast, as they contain no calories. However, sugary melatonin gummies, liquids, and flavored options do contain calories and will halt a fast. The hormone itself can also affect glucose metabolism, making timing and dose important considerations for fasters.

Key Points

Pure Melatonin Does Not Break a Fast: The hormone itself has no caloric value, so a calorie-free capsule or tablet will not technically interrupt your fasting state.
Gummies Contain Sugar: Popular melatonin gummies and flavored options have added sugars, gelatin, and calories, which will break a fast by triggering an insulin response.
Melatonin Affects Blood Sugar: The hormone can influence insulin sensitivity, which may impact blood glucose levels, particularly in individuals with certain genetic factors.
Timing May Matter: Because melatonin affects glucose metabolism, taking large doses or eating when melatonin levels are naturally high could negatively impact your metabolic goals.
Safest Supplement Choices: Opt for pure, unflavored pills or capsules to avoid hidden calories and maintain a strict fast.
Consider Your Fasting Goals: For strict protocols targeting autophagy, avoid all supplements, while a simple calorie-restricted fast is less sensitive to pure melatonin.
Consult a Professional: Always talk to your doctor before adding new supplements, especially if you have health conditions like diabetes, as melatonin can affect blood sugar.

The Core Question: Is Melatonin Itself Caloric?

Pure melatonin, the hormone that regulates your sleep-wake cycle, contains no calories. Because a true fast is defined by the absence of caloric intake, a pure melatonin supplement in a capsule or tablet form will not technically break a fast. This holds true for most traditional fasting protocols, including intermittent fasting (IF). The challenge arises when looking at the various forms of melatonin available on the market, many of which contain added ingredients that are not fast-friendly.

Melatonin Gummies and Other Fast-Breaking Forms

While the hormone itself is fine, many popular melatonin supplements, especially gummies and flavored chews, contain added sugars, corn syrup, gelatin, and other ingredients for flavor and texture. These added calories, even if minimal, are enough to trigger an insulin response and break your fast. For example, some brands of melatonin gummies can contain 15-20 calories or more per serving. To maintain a strict fast, these forms should be avoided entirely during your fasting window.

Melatonin's Impact on Insulin and Glucose Metabolism

Beyond the caloric question, it's important to consider how melatonin interacts with your metabolism on a hormonal level. Research indicates a complex relationship between melatonin and glucose homeostasis, or the regulation of blood sugar.

Melatonin is known to have a suppressive effect on insulin secretion from the pancreas, particularly through its interaction with melatonin receptor 1B (MTNR1B). Studies show that when melatonin levels are high (naturally at night), insulin levels are lower. For individuals with a genetic mutation in the MTNR1B receptor, this effect can be more pronounced, increasing the risk of higher blood sugar levels and insulin resistance. This metabolic process is naturally synchronized with our body's circadian rhythm, but high supplemental doses taken at the wrong time could potentially disrupt this balance.

How Melatonin Interacts with Fasting

When you fast, your body switches from burning glucose for energy to burning fat, a state known as ketosis. Your metabolism is highly sensitive to external inputs during this time. Introducing a high dose of melatonin could potentially alter your metabolic state by impacting insulin secretion, even without calories being present. While studies on this are ongoing, some researchers suggest that eating when melatonin levels are naturally high (e.g., late-night snacking) can worsen glucose management, suggesting the timing of supplement intake is critical. Taking your melatonin dose as close to your natural bedtime as possible, and not immediately before or during your eating window, may be a better strategy.

Comparison Table: Melatonin Supplements and Your Fast

To help you decide, here is a quick guide on popular melatonin supplements and whether they will break a fast.


Supplement Form	Is It Fast-Safe?	Why?	Best Practice for Fasting
Pure Melatonin Capsules/Tablets	Yes (in most cases)	Contains no calories or added sugars. Check ingredients for any non-caloric sweeteners or fillers.	Best choice. Take right before bed to align with natural circadian rhythm.
Melatonin Gummies/Chews	No	Contains sugars and calories that will trigger an insulin response and break a fast.	Avoid entirely during your fasting window.
Melatonin Liquids/Sprays	No (check labels)	Often contain sweeteners, flavors, and other caloric additives. Read the nutritional label carefully.	Avoid unless specifically designed to be zero-calorie and tasteless.
Herbal Teas with Melatonin	No (check labels)	Herbal teas are generally low-calorie, but adding honey, milk, or other sweeteners breaks a fast.	Stick to pure black tea, green tea, or herbal tea without additives.

The Verdict: Fasting Protocols and Your Melatonin Use

The key takeaway is that the type of melatonin matters as much as your fasting goals. For those pursuing a strict fast for metabolic benefits like autophagy, even a slight glucose impact could be counterproductive. For those practicing a more lenient intermittent fasting approach focused on calorie restriction, a non-caloric supplement is likely fine, but a gummy is not.

If you find fasting-induced insomnia to be an issue, some experts suggest using calming herbal teas like chamomile or valerian root to help sleep naturally instead of relying on melatonin supplements, which can alter hormonal balance. Always consult with a healthcare professional to determine the safest course of action, especially if you have an underlying health condition like diabetes.

Conclusion: The Best Approach to Taking Melatonin While Fasting

For those who practice intermittent fasting, understanding how supplements affect your metabolic state is crucial. Pure melatonin in a calorie-free pill or capsule is the safest option for maintaining a fast. Avoid all sugary and flavored forms, such as gummies, as these will undeniably break your fast. Furthermore, consider the hormonal effects of melatonin on insulin and glucose and discuss with your doctor whether a supplement is right for you, especially if you are fasting for specific metabolic benefits. A cautious approach is always best when balancing your sleep and fasting regimen.

For more in-depth scientific research on melatonin and its effect on glucose metabolism, consult sources like the National Institutes of Health.

Frequently Asked Questions

No, a standard, non-caloric melatonin capsule or tablet will not break a fast. Pure melatonin is a hormone without calories. However, always check the ingredients for added fillers or sugars.

Yes, melatonin gummies and other flavored chews contain sugar and calories, which will break your fast. You must avoid these to maintain a strict fasting protocol.

Melatonin can decrease insulin secretion, particularly at night when levels are naturally high. High supplemental doses could potentially disrupt glucose metabolism and cause temporary glucose intolerance, though this is dependent on the individual and dose.

You can take a pure melatonin pill with black coffee or plain tea, as long as no caloric additives like milk, sugar, or cream are used. Black coffee and tea contain negligible calories that are usually acceptable during a fast.

While pure melatonin won't provide calories, its effect on insulin and glucose could potentially impact the deeper metabolic processes of fasting. For maximum fat-burning and autophagy benefits, some advise caution or avoiding it entirely, though research is mixed.

For those seeking an alternative that won't interfere with hormonal balance, calming herbal teas like chamomile or valerian root are good, non-caloric options that can aid with sleep.

Taking melatonin during your eating window is a safe bet to avoid any disruption to your fasting state. However, since melatonin is designed for sleep, taking it right before bed in a non-caloric form is generally considered acceptable and often necessary for sleep.