What is the effect of melatonin on blood glucose levels?

From the Guidelines

Melatonin may have a negative effect on blood sugar levels, particularly in people with diabetes or insulin resistance, as a recent publication described impairment in glucose tolerance among healthy women subsequent to acute melatonin administration 1.

Key Points to Consider

• The effect of melatonin on blood sugar levels is not entirely clear, and more research is needed to fully understand its impact.
• Typical supplemental doses of melatonin range from 1-10 mg taken before bedtime, but for those with diabetes, starting with a lower dose (1-3 mg) is advisable to monitor effects on blood sugar.
• Melatonin may influence insulin secretion through specific receptors in the pancreas and help regulate circadian rhythms that affect glucose metabolism, but its effects vary between individuals, and some studies show mixed results.
• People taking diabetes medications should use caution as melatonin might enhance their blood-sugar-lowering effects, potentially causing hypoglycemia.
• Those with diabetes should monitor their blood glucose levels more frequently when starting melatonin and consult their healthcare provider before beginning supplementation, especially if taking other medications.

Important Considerations for Diabetes Management

• Coordinating food with type of diabetes medicine is crucial, and priority should be given to this aspect of management 1.
• Treatment of hypoglycemia requires ingestion of glucose or carbohydrate-containing food, and glucose is the preferred treatment, although any form of carbohydrate that contains glucose may be used 1.
• Aim for consistent, uninterrupted sleep, even on weekends, as irregular sleep results in poorer glycemic levels 1.

From the Research

Effect of Melatonin on Blood Sugars

• The effect of melatonin on blood sugars has been studied in several research papers, with mixed results 2, 3.
• A systematic review and meta-analysis found that long-term treatment with melatonin did not change fasting glucose significantly, but it reduced fasting insulin levels slightly and trended towards reduced insulin resistance 2.
• Another study found that melatonin stabilizes and strengthens coupling of circadian rhythms, including glucose regulation, although the difference between physiological and pharmacological effects of melatonin is not always clear 3.
• Other studies have investigated the effects of sleep interventions, including melatonin, on glucose metabolism, with inconclusive results 4, 5, 6.
• A randomized controlled trial found that cognitive behavioral therapy for insomnia (CBT-I) improved insomnia symptoms and mood, and perhaps improved glycemic control, in people with type 2 diabetes and insomnia symptoms 6.
• The evidence suggests that melatonin may have beneficial effects on glucose metabolism, but further research is needed to fully understand its effects 2, 3, 4, 5, 6.

Key Findings

• Melatonin reduces fasting insulin levels slightly and trends towards reduced insulin resistance 2.
• Melatonin stabilizes and strengthens coupling of circadian rhythms, including glucose regulation 3.
• Sleep interventions, including melatonin, have inconclusive effects on glucose metabolism 4, 5, 6.
• CBT-I improves insomnia symptoms and mood, and perhaps improves glycemic control, in people with type 2 diabetes and insomnia symptoms 6.

Study Limitations

• The studies had small sample sizes and limited follow-up periods 2, 3, 4, 5, 6.
• The evidence is based on correlations between clinical observations and melatonin secretion, rather than causal relationships 3.
• Further research is needed to fully understand the effects of melatonin on glucose metabolism 2, 3, 4, 5, 6.