MELATONIN & SLEEP: SCIENCE-BACKED, PLAIN-LANGUAGE GUIDE “The brain receives a ‘night signal,’ not a forced ‘sleep command.’” After taking melatonin, the body’s “prepare for night” signal may strengthen. Some people notice relaxation, heavier eyelids, and easier sleep onset. Circadian hormone patterns and thermoregulation can shift toward nighttime physiology. However, responses vary. Taken at the wrong time (especially daytime), it can shift the body clock the wrong way and cause daytime drowsiness. Short-term side effects can include headache, stomach upset, vivid dreams, morning grogginess, and occasionally restlessness. These often improve when dose and timing are adjusted. Combining melatonin with alcohol, sedatives, or certain antidepressants can increase sleepiness; use with anticoagulants may require clinical risk assessment. A practical approach is low dose, correct timing, and a short trial window. If there is no meaningful benefit within 1–2 weeks, increasing dose is not always the answer—light exposure, schedule consistency, and sleep hygiene should be optimized, and persistent severe insomnia should be evaluated medically.