Metformin: The Old Drug in the Longevity Conversation

Metformin is a biguanide that has been the first-line drug for type 2 diabetes for decades. It is not a peptide, but it shows up constantly in self-experimenter circles because of its proposed effects on AMPK signaling, mitochondrial function, and possible longevity benefits. It is also a prescription medication in essentially every jurisdiction, and that matters for how you should approach it.

What it does

Metformin reduces hepatic glucose output and improves insulin sensitivity. Beyond glycemic control, it has been studied for cardiovascular outcomes, cancer incidence in diabetics, and as a candidate "geroprotector." The TAME trial and similar work are ongoing; the longevity case in non-diabetics is suggestive but not settled.

Typical protocol shape

For diabetes, metformin is dosed by a clinician based on glycemic targets and tolerance, typically started low and titrated. For off-label longevity use, the protocol question is contested:

• Some users take low daily doses
• Others avoid it around workouts to preserve exercise adaptations (there is evidence metformin blunts some aerobic gains)
• Extended-release formulations are usually better tolerated than immediate-release

This is a prescription drug. Get it prescribed, and discuss timing with whoever prescribes it.

What to track daily

• Dose and timing
• GI symptoms (diarrhea, nausea, cramping) on a 1 to 5 scale
• Appetite
• Resting heart rate
• Subjective energy, especially around exercise

What to track weekly

• Body weight
• Average GI tolerance score
• Exercise performance versus baseline (subjective and objective)
• Sleep quality

Bloodwork worth doing

Metformin has well-documented bloodwork implications:

• HbA1c every 3 to 6 months
• Fasting glucose and insulin (HOMA-IR if you want a sensitivity proxy)
• Vitamin B12 at baseline and at least annually; metformin reduces B12 absorption
• Comprehensive metabolic panel including kidney function
• Lactate if you have any reason to suspect intolerance (rare but serious)

Realistic expectations

For metabolic markers in people with poor glycemic control, metformin helps. For lean, fit, normoglycemic people taking it for longevity, the measurable changes will often be subtle and may include downsides like blunted training adaptations. Track both sides.

Common mistakes

• Treating it as a supplement rather than a prescription drug
• Ignoring GI symptoms instead of titrating
• Skipping B12 monitoring
• Taking it around hard training sessions if your goal is aerobic adaptation
• Assuming the longevity evidence in mice will replicate in healthy humans

A tracking template

In Peptid AI, log dose with each meal, GI score in the evening, and link weekly weight and any labs you have. Tag training days so you can later look at performance with and without same-day dosing.

Safety notes

Metformin is generally well tolerated but is contraindicated in significant kidney impairment and certain other conditions. Lactic acidosis is rare but serious. Do not start it without a clinician.

Peptid AI is an educational and self-tracking tool. Nothing in this post is medical advice. Doses mentioned reflect what is commonly reported in research literature — they are not recommendations. Always consult a qualified physician before starting, changing, or stopping any protocol.