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Melatonin is a natural hormone released by your brain that regulates your body’s circadian rhythm or internal clock.

Levels increase in response to darkness to promote sleep and decrease in the morning when it’s light to promote wakefulness.

Supplementing with melatonin before bed is a common strategy to alleviate sleeping problems, especially in the elderly who have lower levels compared with their younger counterparts.

While an overall safe and effective sleep aid, melatonin has the potential to cause minor side effects in the elderly.

This article lists three potential melatonin side effects in the elderly and explains how to prevent them.

melatonin side effects in the elderly

1. Trouble waking up

Sleeping in is one of life’s greatest pleasures.

But when sleeping in occurs because you hit the snooze button one too many times, it can negatively impact your day.

Although the evidence is weak, melatonin supplementation may make it difficult for you to wake up.

In one study, older adults with insomnia were randomized to receive 0.4 mg or 4 mg of a sustained-release melatonin supplement 30 minutes before bed for six weeks (1).

A sustained-release melatonin supplement was used to prolong the release of melatonin so that the study’s participants experienced its sleep-promoting properties over a longer period.

At the end of the six-week study period, the older adults who received the higher 4 mg dose of melatonin experienced sustained high levels of melatonin.

Although the researchers didn’t measure melatonin levels after rising, these sustained high levels could extend into the morning hours and make it more difficult for the participants to wake up at their normal time.

However, the potential difficulty in waking up caused by melatonin supplementation can be prevented by supplementing with a smaller dose and choosing a regular melatonin supplement rather than a sustained-release option.

2. Daytime sleepiness

Daytime grogginess or sleepiness is often the result of a poor night’s rest, but it may also be a consequence of melatonin supplementation.

Melatonin levels can remain elevated into waking hours with high doses or sustained-release formulas, which can cause daytime sleepiness (1).

However, this can easily be prevented by taking the lowest dose possible and increasing to a higher dose if needed.

Taking melatonin too late at night can also result in elevated melatonin levels into waking hours, also increasing daytime sleepiness.

Still, the potential residual sleepiness that melatonin supplementation may cause is far less reliable and severe compared with benzodiazepines commonly prescribed for older adults to promote sleep such as estazolam (Prosom), flurazepam (Dalmane), Quazepam (Doral), and Temazepam (Restoril).

In fact, one study found that older adults were able to discontinue their prescribed benzodiazepines for sleep after switching to melatonin (2).

3. Irritability

From life stress to depression to low blood sugar, irritability can be a symptom of many things.

It can also occur as a result of poor sleep.

In one study, older adults — most of whom had dementia — living in long-term care facilities were randomized to receive 2.5 mg of melatonin or a placebo one hour before bed for 15 months (3).

The residents in both groups were also randomized to receive low- or high-intensity ceiling-mounted light exposure from 10 AM to 6 PM.

Increased light exposure during this time has been shown to synchronize circadian rhythms in elderly residents with moderate to severe dementia.

Those who received the melatonin reported increased irritability compared with those who received the placebo.

However, this increase in irritability was alleviated in the elderly residents who also received more ceiling-mounted light exposure.

The study’s authors suggested that the long-term melatonin supplementation may have led to increased daytime melatonin levels and, consequently, increased irritability due to sleepiness.

So while long-term melatonin supplementation has the potential to increase irritability in older adults with dementia living in long-term care, it can be prevented with higher light intensity exposure.

Other side effects

Other side effects have been reported with melatonin supplementation in the elderly but:

These include (4, 5):

  • dizziness
  • headaches
  • nausea
  • constipation
  • diarrhea
  • acid reflux
  • dry mouth
  • stomach discomfort

However, these side effects were either reported to occur as frequent — and sometimes less frequent — with melatonin compared with placebo and therefore cannot be attributed to melatonin.

The benefits of melatonin for the elderly

Despite the potential side effects of melatonin, it’s a very safe and effective sleep aid for the elderly (4).

Several meta-analyses have shown that melatonin supplementation significantly decreases the time it takes to fall asleep, increases total sleep time, and improves sleep quality in older adults, including those with Alzheimer’s and Parkinson’s disease (5, 6, 7, 8).

These sleep benefits can translate to improvements in memory and mood as well as decrease the reliance on commonly prescribed hypnotic drugs, which can increase the risk of falls and fractures and cause severe drowsiness in the elderly (9, 10).

Beyond its effectiveness as a sleep aid, melatonin has also been shown to offer benefits for the elderly.

A review of six studies found that older adults who received melatonin before or after surgery were 37% less likely to experience post-surgery delirium compared with placebo (11).

Delirium is a disturbance in mental abilities that causes confusion and altered thinking.

Patients who develop delirium in the hospital are more likely to develop dementia and need long-term care after being released (11).

However, not all studies support melatonin supplementation for reducing the occurrence of post-surgery delirium (12).

Melatonin also has strong antioxidant properties and may help reduce oxidative damage associated with chronic inflammatory health conditions that commonly occur in the elderly, such as diabetes, heart disease, kidney disease, and arthritis (13, 14).

Melatonin forms and dose

Melatonin is widely available in a variety of forms, including tablets, capsules, gummies, lozenges, and liquid.

Melatonin is typically sold as a single ingredient but may be used in multi-ingredient formulas alongside other sleep aids, such as ashwagandha, magnesium, and valerian root.

Melatonin doses typically range from 300 mcg to 10 mg, but some products provide up to 60 mg.

A review that evaluated the effectiveness of melatonin doses ranging from 0.5 to 10 mg found that dosages between 1 and 6 mg taken 30–60 minutes before bed are the most effective for improving sleep in older adults (15).

Remember, it’s best to start with the lowest dose possible and increase to a higher dose if needed, so start with 1 mg and increase from there.

Opt for a standard melatonin supplement as they are quick release and are less likely to make waking up difficult like sustained or extended-release options may do.

Melatonin supplements that are sustained or extended-release will say so on the label.

Find melatonin online.

The bottom line

Melatonin is a natural hormone that regulates your sleep-wake cycles.

Older adults have lower levels of melatonin compared with younger adults and may experience sleeping problems as a result.

Melatonin supplements, while generally safe and effective, may make it more difficult to wake up in the morning and cause daytime sleepiness and irritability. However, these side effects are minor and can be reduced or prevented.

The optimal dose for older adults ranges between 1 and 6 mg, but it’s best to start with 1 mg and increase if needed.


Gavin Van De Walle, MS, RD
Gavin Van De Walle, MS, RD

Gavin Van De Walle, MS, RD is a registered dietitian with a master's of science in human nutrition and bioenergetics. Gavin specializes in nutrition for older adults and regulations surrounding long-term care as they relate to food and nutrition.