The Role of Melatonin After 40

Melatonin is the body's darkness signal—the hormone produced by the pineal gland in response to diminishing light, which tells the body it's time to prepare for sleep. Like many hormones, melatonin production declines with age, and this decline is relevant to the sleep difficulties many perimenopausal women experience. But melatonin supplementation is often misunderstood—used at the wrong doses, for the wrong reasons, in ways that don't match its actual physiology.

How Melatonin Works

Melatonin doesn't cause sleep—it doesn't have sedative properties in the way that sleep medications do. What it does is signal the brain that nighttime has arrived and it's time to begin the physiological preparation for sleep: lowering core body temperature, reducing alertness, and shifting the body toward rest. This signal is most important for setting and maintaining circadian rhythm—the internal clock that determines when you feel sleepy and when you feel alert.

Melatonin production begins to decline in the mid-40s in many women, and disruption to its normal nighttime rise—caused by artificial light exposure, particularly from screens—is one of the most common and most modifiable contributors to sleep difficulty in midlife.

What the Evidence Says About Supplementation

Melatonin supplementation has the strongest evidence for: resetting circadian rhythms (jet lag, shift work), sleep onset insomnia (difficulty falling asleep), and age-related melatonin decline. It is less effective for the type of sleep maintenance insomnia—frequent awakenings—that is most common in perimenopause. This means melatonin may help you fall asleep but is less likely to keep you asleep through the night if your awakenings are driven by hot flashes, cortisol, or progesterone deficiency.

Dosing Matters

Most melatonin supplements sold in the US are dramatically overdosed relative to what the research supports. Physiological doses—the range that mimics what the body would naturally produce—are 0.5mg to 1mg, taken 30–60 minutes before intended sleep onset. The 5mg, 10mg, and even 20mg doses commonly sold in pharmacies are pharmacological doses that can actually disrupt circadian rhythm with regular use. Start low, and resist the urge to increase just because you can buy a higher dose over the counter.

Blue-light blocking glasses worn in the 2 hours before bed, combined with dimming household lights in the evening, can significantly support natural melatonin production without any supplementation—and are often more effective for sleep onset than melatonin tablets.