What are the benefits of taking metformin in the morning?

Taking metformin in the morning may align its effects with the body’s daily rhythms and support glucose regulation during the day, but these benefits are presented as potential rather than established. 1

• Daytime NAD+: The rationale for morning timing is that NAD levels naturally rise in the morning and follow a circadian cycle. 2
• Insulin sensitivity and glucose regulation: Metformin can improve insulin sensitivity, and its glucose-lowering effect may vary depending on the time it is taken; evidence discussed includes a timing study in mice, with human implications left uncertain. 3
• Exercise performance: Morning dosing could leave more distance from later exercise, but the practical point described is that metformin may reduce stamina; Sinclair said he skips it on days he exercises to get the most from his workout. 4
• Longevity associations: In an observational study of people with type 2 diabetes taking metformin, researchers reported a 15% relative reduction in all-cause mortality over a median 2.8-year follow-up; this is an association, not proof that metformin causes longevity benefits. Sinclair also cited possible protection against cancer, heart disease, frailty, and dementia. 5