Does Melatonin Expire? Shelf Life, Storage and Expired Melatonin

Yes, melatonin expires. The date on the bottle is the manufacturer's promise that the product still holds the amount on the label, and after that date there is no guarantee it does. Lab studies show melatonin itself is a fairly stable molecule: compounded capsules and a liquid kept more than 98% of their melatonin over 90 days (Haywood et al., 2009), while heat, light and alkaline conditions break it down faster (Pranil et al., 2020). Expired melatonin is unlikely to turn harmful, but it may be weaker than you expect, and the FDA advises against using any expired medicine (FDA). This guide explains what the date means, how long melatonin lasts in each form, how to store it, and what to do with an old bottle.

It is educational, not medical advice.

Key Takeaways

• The date is about strength: the FDA says expired products can be less effective because of a change in chemical composition or a decrease in strength, and once the date has passed there is no guarantee a product is safe and effective (FDA).
• Melatonin is fairly stable: sterile melatonin solutions showed no loss of potency for up to 6 months at fridge or freezer temperature in one study (Cavallo and Hassan, 1995), and compounded 3 mg capsules stayed above 98% for 90 days (Haywood et al., 2009).
• Heat, light and pH matter: melatonin broke down faster at higher temperatures and pH, and light sped up its loss in fruit juice (Pranil et al., 2020).
• Labels already vary: in a test of 31 supplements, melatonin content ranged from 83% below to 478% above the label (Erland and Saxena, 2017), so an old or badly stored bottle adds more uncertainty.
• What to do: store it cool, dry and closed, check the date before each new bottle, and replace it once it has expired.

Does Melatonin Expire?

Yes. Every melatonin product carries a date, often marked "EXP" or "best by", printed on the label or stamped on the bottle. The FDA explains that the expiration date on a medicine is a critical part of deciding whether it is safe to use and will work as intended, and that expired products can be less effective or risky because their chemistry changes or their strength falls (FDA). That guidance is written for medicines, but the same logic applies to a melatonin product: the date marks how long the maker stands behind the amount on the label.

Melatonin is the hormone your brain makes in response to darkness (NCCIH). As a molecule it holds up reasonably well, which is why the main risk with an old bottle is a weaker dose rather than a dangerous one. Our melatonin ingredient page covers how it works in the body.

How Long Does Melatonin Last in Each Form?

Form	What the studies show	What can shorten it
Capsules and tablets	Compounded 3 mg capsules kept more than 98% of their melatonin for 90 days, including at 40 degrees C and 75% humidity	Damp storage, a cabinet near the shower or stove
Liquids and sprays	A compounded liquid stayed above 98% for 90 days at 4 or 25 degrees C; sterile solutions showed no loss for up to 6 months in the fridge or freezer	Heat, light, alkaline pH, an open or contaminated bottle
Gummies	Not tested in the studies above	Heat and humidity, which also change texture

The capsule and liquid figures come from a pharmacy study that stored melatonin in amber glass bottles and tested it at 7, 14, 28, 60 and 90 days (Haywood et al., 2009). The 6 month figure comes from research solutions prepared in sterile vials and kept at 4 degrees C or minus 70 degrees C (Cavallo and Hassan, 1995). In another study, melatonin in solution showed no loss in the first 2 days at room temperature or body temperature, then a gradual decline of up to about 30% over 21 days across a wide pH range (Daya et al., 2001). Commercial products add their own ingredients and packaging, which is why the maker's date, based on its own testing, is the figure to follow.

What Happens If You Take Expired Melatonin?

Most likely, you get less melatonin than the label says. The FDA's warning is that there is no guarantee an expired product is safe and effective, and its advice is simple: if your medicine has expired, do not use it (FDA).

With melatonin there is a second reason for care. Even in date, supplements vary: a study of 31 products found melatonin content from 83% below to 478% above the label, with as much as 465% difference between lots of the same product, and 8 products also contained serotonin (Erland and Saxena, 2017). An expired bottle adds another unknown on top of that, which makes it harder to judge whether a dose is working.

Signs a bottle should go regardless of the date include a changed color or smell, clumping or stickiness in capsules or gummies, cloudiness or particles in a liquid, or a cracked seal. If you have taken a dose from an old bottle, there is no need to panic, but replace it and watch for the usual melatonin side effects, which in short-term adult studies were mild, such as headache, dizziness, nausea and sleepiness (NCCIH). Our guide to melatonin side effects covers who should avoid it.

How to Store Melatonin So It Lasts

1. Keep it cool and dry. The FDA suggests a dresser drawer, storage box, closet shelf or kitchen cabinet away from hot appliances and the sink, and warns that a damp bathroom cabinet can reduce effectiveness before the date (FDA).
2. Keep it out of light and heat. Melatonin broke down faster with heat and light in lab tests (Pranil et al., 2020), so leave it in its original bottle and out of a hot car or sunny windowsill.
3. Close it after every use. A tight cap keeps out moisture and air. For a nasal spray, keep the tip clean and the cap on, and do not share the bottle.
4. Follow the label. Some products have their own storage directions; those come first.
5. Keep it away from children, who may mistake gummies for candy.

How to Get Rid of Expired Melatonin

The FDA prefers a drug take-back location or a pre-paid mail-back envelope for expired or unwanted medicines. If neither is available, follow its instructions for throwing medicine away in your household trash (FDA). Read your product label first in case it includes its own disposal directions.

How Much Melatonin Do You Need, and When?

An expiry date is only one part of getting melatonin right. Our melatonin dosage guide covers how much to take, how long melatonin lasts in your body explains timing and next-day grogginess, and melatonin and alcohol covers evening drinks. If you would rather get a little from food, see foods with melatonin, and if you prefer to skip it, see sleep supplements without melatonin. For spray amounts and timing, see our guide to melatonin spray dosage.

Where Our Products Fit

Our Melatonin Nasal Spray provides 200 mcg of melatonin with L-theanine per two-spray serving, 30 servings per bottle. Use one spray in each nostril while gently inhaling through your nose, with your head tilted back slightly, and leave it for at least 60 seconds before blowing your nose. Keep the bottle closed and stored as directed on the label, and check the date when a new bottle arrives. It is absorbed through the lining of the nose instead of being swallowed like a capsule, so some of each dose skips digestion.

The Sleep Stack pairs it with Theanine Nasal Spray and Lithium Orotate in one bedtime routine. Learn more on our melatonin ingredient page, the sleep health hub and the Melatonin Nasal Spray FAQ.

When to Talk to a Doctor

Talk with your doctor or pharmacist before using melatonin if you are pregnant or breastfeeding, take medication, or have ongoing trouble sleeping despite good habits. There has been little research on melatonin in pregnancy and breastfeeding (NCCIH).

Frequently Asked Questions

Does melatonin expire?

Yes. The date on the label marks how long the maker guarantees the amount listed. After it, there is no guarantee the product is still at full strength, and the FDA advises against using expired medicines (FDA).

Is it safe to take expired melatonin?

Expired melatonin is more likely to be weaker than harmful, but there is no guarantee either way once the date has passed, so the safer choice is to replace it (FDA).

How long is melatonin good for after the expiration date?

There is no reliable figure for commercial products. Lab studies show melatonin can stay stable for months under controlled conditions (Haywood et al., 2009) (Cavallo and Hassan, 1995), but your bottle's own date is the only tested promise.

Does melatonin lose its strength over time?

It can. In solution, melatonin declined by up to about 30% over 21 days at room or body temperature, and heat and light sped up its loss in other tests (Daya et al., 2001) (Pranil et al., 2020).

Does expired melatonin still work?

It may work less well, and you cannot tell how much melatonin is left. If a familiar dose seems weaker, an old bottle is one reason to check.

Should melatonin be refrigerated?

Only if the label says so. Most products are kept in a cool, dry place at room temperature, away from heat, light and humidity.

Do melatonin gummies expire faster?

Gummies were not part of the studies above, but heat and humidity change their texture, and a sticky or melted gummy is a sign to replace the bottle.

How do I dispose of old melatonin?

Use a drug take-back location or a mail-back envelope if you can; otherwise follow the FDA's steps for throwing medicine away at home (FDA).

Sources

1. U.S. Food and Drug Administration. Don't Be Tempted to Use Expired Medicines. FDA
2. Haywood A, Burrell A, van Breda K, et al. Stability of melatonin in an extemporaneously compounded sublingual solution and hard gelatin capsule. Int J Pharm Compd. 2009. PubMed 23970011
3. Cavallo A, Hassan M. Stability of melatonin in aqueous solution. J Pineal Res. 1995. PubMed 7629696
4. Daya S, Walker RB, Glass BD, et al. The effect of variations in pH and temperature on stability of melatonin in aqueous solution. J Pineal Res. 2001. PubMed 11555171
5. Pranil T, Moongngarm A, Loypimai P. Influence of pH, temperature, and light on the stability of melatonin in aqueous solutions and fruit juices. Heliyon. 2020. PubMed 32258489
6. Erland LA, Saxena PK. Melatonin natural health products and supplements: presence of serotonin and significant variability of melatonin content. J Clin Sleep Med. 2017. PubMed 27855744
7. National Center for Complementary and Integrative Health. Melatonin: What You Need To Know. NCCIH

Our products are not intended to diagnose, treat, cure or prevent any disease. This article is for education only and is not medical advice.