Melatonin for Diabetes: Does It Help?

meta-analysis PMID: 40698248

Quick Summary: Research suggests that taking melatonin might help people with type 2 diabetes slightly lower their blood sugar levels. This study looked at several smaller studies and found that melatonin could lead to small improvements in blood sugar control.

Does Melatonin Help Lower Blood Sugar?

This research looked at multiple studies to see if melatonin could help people with type 2 diabetes manage their blood sugar. The results showed that melatonin supplementation led to:

Lower Fasting Blood Sugar (FBG): People taking melatonin had, on average, about 8 mg/dL lower blood sugar when they hadn't eaten.

Lower HbA1c: This is a measure of average blood sugar over 2-3 months. Melatonin users saw a reduction of about 0.31%.

Study Details

Who was studied: Adults with type 2 diabetes.

How long: Studies lasted between 8 to 24 weeks (about 2 to 6 months).

What they took: Melatonin, usually 5 mg, taken once a day before bed.

What This Means For You

Potential Benefit: Melatonin might help slightly improve blood sugar control if you have type 2 diabetes.

Not a Replacement: This study doesn't suggest that melatonin should replace your current diabetes medications.

Talk to Your Doctor: Always talk to your doctor before starting any new supplement, including melatonin, especially if you have diabetes. They can help you decide if it's right for you and monitor any potential interactions with your current medications.

Dosage: If your doctor approves, the most common dose used in the studies was 5mg taken before bed.

Study Limitations

More Research Needed: The study looked at a few smaller studies. Larger studies are needed to confirm these findings.

Varied Results: The studies had some differences, like the doses of melatonin used and how long people took it.

Not a Huge Impact: The changes in blood sugar were relatively small.

Other Factors: The studies didn't always account for other things that affect blood sugar, like diet and exercise.

Key Findings

This meta-analysis concluded that melatonin supplementation significantly improved fasting blood glucose (FBG) and hemoglobin A1c (HbA1c) levels in patients with type 2 diabetes mellitus (T2DM). The pooled analysis showed a mean reduction in FBG of −8.24 mg/dL (95% CI: −12.61 to −3.87; p < 0.001) and in HbA1c of −0.31% (95% CI: −0.52 to −0.10; p = 0.004). No significant effects were observed for insulin resistance (HOMA-IR) or fasting insulin levels. The authors assert that melatonin may be a viable adjunct therapy for glycemic control in T2DM, though larger trials are needed to confirm clinical applicability.

Study Design

This was a systematic review and meta-analysis of randomized controlled trials (RCTs). The study included 7 RCTs with a total of 428 participants diagnosed with T2DM. Trials were identified via PubMed, Embase, and Cochrane Library databases (search cutoff: December 2024). Inclusion criteria required RCTs comparing melatonin supplementation versus placebo in T2DM patients, with outcomes including FBG, HbA1c, fasting insulin, or HOMA-IR. Study durations ranged from 8 to 24 weeks, with most (5/7) lasting 12–16 weeks. Participant demographics were limited to adults (mean age 50–65 years), but sex distribution and ethnicity were not consistently reported across studies.

Dosage & Administration

Melatonin was administered orally at doses ranging from 2 mg to 10 mg daily. The majority of trials (5/7) used 5 mg/day, administered as a single dose 30–60 minutes before bedtime. Two studies tested 2 mg/day and 10 mg/day, respectively. All formulations were immediate-release tablets. Duration of supplementation aligned with trial lengths (8–24 weeks).

Results & Efficacy

FBG: Significant reduction of −8.24 mg/dL (95% CI: −12.61 to −3.87; I² = 68%, p < 0.001).
HbA1c: Significant reduction of −0.31% (95% CI: −0.52 to −0.10; I² = 52%, p = 0.004).
Fasting Insulin: Non-significant change (−0.87 μIU/mL; 95% CI: −2.12 to 0.38; p = 0.17).
HOMA-IR: Non-significant change (−0.21; 95% CI: −0.65 to 0.23; p = 0.35).
Heterogeneity was moderate to high (I² > 50%) for all outcomes, suggesting variability in trial methodologies. Subgroup analysis indicated dose-dependent effects, with 5 mg/day yielding the most consistent FBG improvements.

Limitations

Key limitations include high heterogeneity across studies (differing doses, durations, and baseline patient characteristics), small sample sizes per trial (median n = 52), and incomplete demographic reporting (e.g., sex, ethnicity, diabetes duration). Publication bias was suspected via funnel plot asymmetry for HbA1c (p = 0.03 in Egger’s test). Most trials lacked data on long-term safety, concomitant medications, or lifestyle factors (diet/exercise). Future research requires standardized protocols, longer durations (>6 months), and diverse populations to assess real-world applicability.

Clinical Relevance

For T2DM patients, melatonin (particularly 5 mg/day at bedtime) may offer modest adjunctive benefits for glycemic control, potentially reducing FBG by ~8 mg/dL and HbA1c by 0.3%. However, effects are not clinically transformative (e.g., HbA1c reductions <0.5% are generally considered subtherapeutic per ADA guidelines). Patients should not replace standard diabetes medications with melatonin. Those using melatonin for sleep should monitor glucose levels, as interactions with antidiabetic drugs (e.g., insulin sensitizers) are plausible but unstudied here. Consultation with a healthcare provider is essential before initiating supplementation.