LEF Life Extension Foundation doctors have been advocating low dose Metformin with meals to keep insulin receptors sensitive healthy as we age. There is a fair amount of peer reviewed research supporting this.
The Last part is what would concern me if your on any PH, Oral AAS or Drink alcohol.
Precaution: There was a drug that was very similar to metformin, called phenformin, which was removed from the market by the FDA in 1976. Some physicians gave this drug to patients with kidney or liver problems, or congestive heart failure. Some of these patients died due to lactic acidosis build-up because a healthy kidney and liver were needed to metabolize the drug. It is not recommended that people who have liver or kidney problems, or congestive heart failure, use metformin due to the drug's similarities to phenformin. Those who drink excessive amounts of alcohol should not take metformin.
I took it now and then when I was on HGH but I wasn't on any oral aas and I knew not to take it on my bourbon night if it did anything for me, it wasn't anything I could tell. I feel like taking too many drugs at once, if you're not competing in anything, is prob getting your system all "tangled up" and best to keep a simple stack.