From the Research
Melatonin is unlikely to cause feelings of muscle weakness the next day, as the most recent and highest quality study found no significant changes in muscle strength in postmenopausal women taking melatonin compared to a placebo group. This study, published in 2025, investigated the effects of 12-week melatonin supplementation on motor skills, including muscle strength, manual dexterity, and static postural balance, in patients with multiple sclerosis 1. The results showed that melatonin supplementation actually improved knee muscle strength, manual dexterity, and static postural balance in these patients.
While some individuals may experience a "hangover effect" from melatonin, characterized by feelings of grogginess or lethargy the next day, this is not typically associated with muscle weakness. Typical melatonin doses range from 0.5-10 mg taken 30-60 minutes before bedtime, with lower doses (0.5-3 mg) often being sufficient and potentially causing fewer next-day effects. If you're experiencing unusual side effects after taking melatonin, consider consulting with a healthcare provider to rule out any underlying conditions or unusual sensitivity to melatonin.
It's worth noting that melatonin has been shown to have antioxidant and anti-inflammatory properties, which may actually help protect against muscle damage and weakness 2. Additionally, melatonin has been found to improve sleep quality and duration, which is essential for muscle recovery and repair 3. Overall, the current evidence suggests that melatonin is unlikely to cause muscle weakness, and may even have beneficial effects on muscle function and overall health.