What Causes Low Melatonin?

Low melatonin results from a surprisingly wide range of causes, from the light hitting your eyes after dark to the medications in your cabinet and the gradual calcification of the tiny gland that produces it. Melatonin is synthesized primarily in the pineal gland during nighttime hours, and anything that disrupts that process, whether environmental, pharmacological, nutritional, or structural, can drag levels down. Some of these causes are well within your control, while others are baked into biology.

Nighttime Light Exposure

The single most common reason for suppressed melatonin in modern life is artificial light after dark. Your pineal gland takes its cue from darkness: when photoreceptors in the retina detect light, they send a signal through the brain that tells the pineal gland to hold off on melatonin production. This system evolved under conditions where sunset meant actual darkness, so it is exquisitely sensitive to light at night, particularly light in the short-wavelength blue range. Exposure to blue-appearing light between roughly 446 and 477 nanometers produces a strong, dose-dependent suppression of plasma melatonin in healthy people.

1American Physiological Society (J Appl Physiol). Blue light from light-emitting diodes elicits a dose-dependent suppression of melatonin in humans

This matters because phones, tablets, laptops, and LED overhead lighting are rich in exactly those wavelengths. You do not need to stare at a screen for hours; even moderate room lighting at night can blunt the melatonin rise your body would otherwise produce. In a controlled study of simulated shift-work conditions, unfiltered bright light at 800 lux drastically suppressed melatonin, while the same brightness filtered to block wavelengths below 530 nanometers preserved melatonin at levels comparable to dim-light conditions.

2The Journal of Clinical Endocrinology & Metabolism. Blocking Low-Wavelength Light Prevents Nocturnal Melatonin Suppression with No Adverse Effect on Performance during Simulated Shift Work

The practical upshot is that if your evenings involve brightly lit rooms and screen time right up to bedtime, your melatonin levels are almost certainly lower than they would be otherwise. Blue-light-filtering glasses, dimmer evening lighting, and screen settings that shift color temperature after sunset are all partial countermeasures. Complete darkness is the gold standard, but most people compromise with something in between.

Aging and Pineal Calcification

Melatonin production declines with age, and the mechanism appears to be partly structural. The pineal gland accumulates calcium deposits over the course of a lifetime, a process sometimes visible on brain scans as a bright spot. A postmortem study spanning ages from three months to 65 years found that calcium deposits in the pineal gland rose with age and that higher nighttime calcium in the gland correlated with lower melatonin content.

3PubMed. Calcium, calcification, and melatonin biosynthesis in the human pineal gland: a postmortem study into age-related factors

This calcification appears to compromise the gland’s ability to synthesize melatonin and has been linked to a range of neurological problems.

4PubMed Central. Pineal Calcification, Melatonin Production, Aging, Associated Health Consequences and Rejuvenation of the Pineal Gland

The age-related decline is one reason older adults commonly report lighter, more fragmented sleep. It is also part of why melatonin supplements have gained popularity among people over 50. The decline is gradual and starts earlier than most people assume; it does not suddenly switch off at retirement age but erodes across decades.

Puberty Brings Its Own Drop

The melatonin decline is not exclusively a phenomenon of old age. Children produce the highest levels of melatonin, and those levels begin falling during puberty. A systematic review and meta-analysis found that advancing Tanner stages (the standard measure of pubertal development) were associated with decreasing average and peak melatonin concentrations.

5PubMed. Melatonin secretion across puberty: A systematic review and meta-analysis

Earlier research measuring peak melatonin across pubertal stages found values dropping from around 154 pg/mL in prepubertal children to about 117 pg/mL in later puberty. That said, age and pubertal stage are closely tangled together. When researchers statistically controlled for age, the independent effect of puberty on melatonin weakened considerably, suggesting that the decline may track with general maturation rather than puberty-specific hormonal changes.

6Neuroendocrinology. Plasma Melatonin Rhythm in Normal Puberty: Interactions of Age and Pubertal Stages

For parents wondering why their teenager suddenly cannot fall asleep at a reasonable hour, this biological melatonin dip is part of the picture, compounded by the fact that teenagers tend to saturate themselves with screen light in the evening.

Medications That Suppress Melatonin

Several widely used drug classes reduce melatonin production, and most people taking them have no idea this is happening.

Beta-Blockers

Beta-blockers, prescribed for high blood pressure, heart rhythm problems, and anxiety, are among the clearest pharmacological causes of low melatonin. The mechanism is direct: the pineal gland relies on signals from the sympathetic nervous system, delivered through beta-1 adrenergic receptors, to ramp up melatonin synthesis at night. Beta-blockers sit on those receptors and prevent the signal from getting through. Research has confirmed that only the active, beta-blocking forms of drugs like propranolol and atenolol reduce nocturnal melatonin, while the inactive forms have no effect, pinning the cause squarely on beta-1 receptor blockade.

7PubMed. Influence of beta-blockers on melatonin release

This is clinically relevant because sleep disturbance is one of the most common complaints among people on beta-blockers, and the melatonin connection is a likely explanation. Some clinicians now recommend low-dose melatonin supplementation alongside beta-blocker therapy to offset this effect.

8PubMed Central. Night-time exogenous melatonin administration may be a beneficial treatment for sleeping disorders in beta blocker patients

NSAIDs and Painkillers

Common over-the-counter painkillers like ibuprofen and aspirin can also suppress melatonin. These drugs work by inhibiting prostaglandin synthesis, and prostaglandins turn out to be involved in the melatonin production pathway. In controlled trials, nighttime melatonin levels dropped after NSAID use compared to placebo.

9PubMed. Nonsteroidal anti-inflammatory drugs alter body temperature and suppress melatonin in humans

The effect is not trivial. One study found that the NSAID ketoprofen cut average melatonin secretion over a four-hour window by roughly half.

10PubMed. Analgesic effects on endogenous melatonin secretion

The opioid buprenorphine also reduced melatonin secretion in the same study, suggesting that the suppressive effect extends beyond NSAIDs to other analgesic classes. If you regularly take ibuprofen or aspirin in the evening for pain relief and also struggle with sleep, the melatonin connection is worth considering. A different type of pain medication, or taking it earlier in the day, could make a difference.

Caffeine and Alcohol

Two of the most widely consumed substances on earth both interfere with melatonin, though in different ways.

Caffeine suppresses nighttime melatonin levels and disrupts the normal drop in body temperature that accompanies sleep onset. In a controlled study, a 200-milligram caffeine dose (roughly the amount in a strong cup of coffee) taken during overnight wakefulness lowered melatonin and flattened the temperature rhythm.

11PubMed. Caffeine and light effects on nighttime melatonin and temperature levels in sleep-deprived humans

Caffeine also shifts the timing of your melatonin rhythm. A double-blind study found that a dose equivalent to a double espresso consumed three hours before bedtime pushed the melatonin rhythm back by about 40 minutes, working through an adenosine receptor pathway that feeds into the molecular clock.

12PubMed Central. Effects of caffeine on the human circadian clock in vivo and in vitro

Alcohol tells a similar story with different chemistry. In a dose-dependent, double-blind crossover study, evening alcohol intake suppressed nocturnal melatonin by about 41% at midnight compared to control conditions.

13The Journal of Clinical Endocrinology & Metabolism. Ethanol inhibits melatonin secretion in healthy volunteers in a dose-dependent randomized double blind cross-over study

A separate study in young adults confirmed the finding with a more moderate dose, showing melatonin reductions of about 15 to 19% within a few hours of drinking.

14PubMed. Evening alcohol suppresses salivary melatonin in young adults

The popular notion that a glass of wine helps you sleep is therefore partially backward. Alcohol may make you feel drowsy, but it is simultaneously suppressing one of the hormones your body uses to maintain deep, restorative sleep cycles. The result is often fragmented sleep in the second half of the night, once the sedative effect wears off and the melatonin deficit remains.

Tryptophan and Nutritional Shortfalls

Melatonin is built from tryptophan, an essential amino acid your body cannot make on its own. Tryptophan is first converted to serotonin, which is then converted to melatonin. If tryptophan availability drops, melatonin production follows. In a randomized, double-blind experiment, acute tryptophan depletion reduced plasma tryptophan to less than 20% of baseline, and melatonin secretion fell in every single participant.

15The Journal of Clinical Endocrinology & Metabolism. Effects of acute tryptophan depletion on nocturnal melatonin secretion in humans

Under normal dietary conditions, severe tryptophan deficiency is uncommon in wealthy countries, but diets that are very low in protein, highly restrictive, or heavily processed can fall short. Beyond tryptophan itself, the conversion steps require cofactors including B vitamins and magnesium. A review of the dietary factors influencing melatonin levels concluded that foods providing tryptophan, as well as vitamins and minerals needed as cofactors in the melatonin synthesis pathway, can meaningfully modulate melatonin output.

16PubMed Central. Dietary factors and fluctuating levels of melatonin

This does not mean you need to megadose any single nutrient. It means that consistently poor nutrition, especially protein-deficient diets, could be quietly dragging down your melatonin. Foods naturally rich in tryptophan include poultry, eggs, dairy, nuts, and seeds.

Stress and Shift Work

Chronic stress interferes with melatonin through several overlapping pathways. Stress activates the hypothalamic-pituitary-adrenal axis, flooding the body with cortisol, and the cortisol and melatonin systems appear to interact in ways that are not fully untangled but clearly push in opposite directions. Animal research has shown that chronic stress deteriorates the normal circadian pattern of melatonin release and that melatonin and corticosterone (the rodent equivalent of cortisol) correlate negatively during nighttime hours.

17PubMed. Circadian patterns of melatonin, corticosterone, and progesterone in male rats subjected to chronic stress: effect of constant illumination

In humans, occupational stress and night-shift work converge to create especially harsh conditions for melatonin. A systematic review found that night-shift nurses had significantly lower nocturnal melatonin concentrations than their day-shift counterparts, confirming a direct suppressive effect of occupational stress and shifted schedules on pineal output.

18PubMed Central. Melatonin and Cortisol Suppression and Circadian Rhythm Disruption in Burnout Among Healthcare Professionals: A Systematic Review

Shift workers face a double hit: the light exposure during nighttime hours directly suppresses melatonin, and the chronic physiological stress of fighting the body’s circadian clock further impairs the system. If you work rotating or overnight shifts and feel that your sleep never fully recovers even on your days off, suppressed melatonin production is a major reason why.

Depression and Low Melatonin

The relationship between depression and melatonin is a classic chicken-and-egg problem, but the association is consistent. In a cross-sectional study, patients with major depressive disorder had lower nocturnal melatonin levels than healthy controls, and their peak melatonin was reached later in the night.

19PubMed Central. Morning and nocturnal serum melatonin rhythm levels in patients with major depressive disorder: an analytical cross-sectional study

A study in patients with multiple sclerosis found the same pattern: those with comorbid major depression had nocturnal melatonin levels that averaged roughly 21 pg/mL, compared to about 52 pg/mL in MS patients without depression.

20PubMed. The association of nocturnal serum melatonin levels with major depression in patients with acute multiple sclerosis

Whether depression causes the melatonin drop, or the melatonin drop worsens depression, or both run in parallel driven by a common upstream problem, remains an open question. The pharmaceutical industry has leaned into the connection: agomelatine, an antidepressant that works partly through melatonin receptors, was developed on the premise that restoring melatonin signaling has mood-related benefits. For anyone dealing with depression and poor sleep simultaneously, the melatonin angle is worth raising with a clinician.

Neurodegenerative Disease and Receptor Loss

In Alzheimer’s disease, the problem extends beyond melatonin production to the brain’s ability to respond to it. The suprachiasmatic nucleus, the brain’s master clock, contains melatonin receptors that help synchronize circadian rhythms. Research on postmortem brain tissue found that both the number of melatonin receptor-expressing neurons and other clock-related neurons in the suprachiasmatic nucleus were sharply reduced in advanced Alzheimer’s (late neuropathological stages), though not in the earliest stages.

21PubMed. Decreased MT1 melatonin receptor expression in the suprachiasmatic nucleus in aging and Alzheimer’s disease

This receptor loss helps explain the severe circadian disruption commonly seen in Alzheimer’s patients, including “sundowning,” the agitation and confusion that worsens in the evening. Even if the pineal gland is still producing some melatonin, the brain’s clock can no longer respond to it properly. The finding also raises questions about why melatonin supplementation trials in Alzheimer’s patients have yielded mixed results: if the receptors are gone, simply adding more melatonin to the bloodstream may not help much.

Structural Problems in the Pineal Gland

Physical damage to or around the pineal gland can directly eliminate melatonin production. Pineal cysts, which are relatively common incidental findings on brain imaging, usually do not affect melatonin levels when the gland tissue itself is intact. However, a case report described a 14-year-old with a large pineal cyst who had a blunted nocturnal melatonin peak, lower total melatonin output, and an inability to maintain a normal sleep-wake schedule.

22PubMed Central. Non-24-Hour Sleep-Wake Rhythm Disorder and Melatonin Secretion Impairment in a Patient With Pineal Cyst

More dramatically, surgical removal of a pineal cyst effectively eliminates melatonin production altogether. A study comparing patients before and after pineal cyst resection found that pre-surgical patients had a normal melatonin rhythm, but post-surgical patients had flatlined melatonin levels throughout the entire 24-hour cycle, equivalent to having had the pineal gland removed entirely.

23PubMed. Melatonin and cortisol secretion profile in patients with pineal cyst before and after pineal cyst resection

Pineal tumors, though rare, can have similar effects. And in at least one documented case, a small neuroepithelial cyst in the pineal gland was associated with a low peak melatonin level and nocturnal headaches.

24PubMed. Nocturnal headache associated with melatonin deficiency due to a pineal gland cyst

If you have been told you have a pineal cyst on a brain scan, the odds are good that it is benign and not affecting your melatonin. But if you also have severe, otherwise-unexplained sleep-wake disruption, it is worth discussing with a neurologist.

Genetic Variations in the Melatonin Pathway

Some people are genetically predisposed to produce less melatonin. The final step in melatonin synthesis is carried out by an enzyme called ASMT. Screening of the gene encoding this enzyme in a large sample of patients with intellectual disability turned up mutations that were associated with significantly lower enzyme activity compared to controls.

25PubMed Central. Mutation screening of ASMT, the last enzyme of the melatonin pathway, in a large sample of patients with intellectual disability

Variants in the MTNR1B gene, which codes for a melatonin receptor, have also attracted attention in metabolic research. In a large prospective study, women with lower melatonin secretion (measured via a urinary metabolite) had greater insulin resistance than those with higher secretion.

26JAMA. Melatonin Secretion and the Incidence of Type 2 Diabetes

Genetic causes of low melatonin are not something most people can test for outside a research setting, but they help explain why some individuals seem to be “bad sleepers” from birth despite good habits. They also underscore the metabolic stakes: melatonin is not just a sleep hormone, and genetic shortfalls in its production or signaling may ripple into blood sugar regulation and beyond.

The Gut Connection

An emerging area of research suggests that the gut microbiome plays a role in melatonin levels throughout the body. While the pineal gland gets most of the attention, the gut actually produces substantial amounts of melatonin on its own. Recent work in mice demonstrated that animals treated with antibiotics (wiping out their gut bacteria) or raised germ-free had diminished melatonin levels in their blood. Fecal microbiota transplantation helped restore those levels, confirming the microbiome’s influence on circulating melatonin.

27PubMed Central. Gut microbiota regulates host melatonin production through epithelial cell MyD88

This research is still in its early stages and the findings are mostly from animal models, so it is too soon to draw firm conclusions for humans. But it does open intriguing questions about whether antibiotic use, chronic gut inflammation, or dysbiosis could contribute to low melatonin. If future studies confirm the link, it would add gut health to the already long list of factors that shape how much melatonin your body produces each night.