Type 2 diabetics on metformin live 15% longer than non-diabetics. This is remarkable considering how big a health disadvantage diabetes itself is.
Metformin seems to mimic fasting somehow, by interfering with mitochondrial function.
For more information I refer you to David Sinclair's numerous discussions on this topic. He takes 1 gram of metformin per day with his evening meal.
This is not medical advice.