Biguanide

Metformin

Also known as: Glucophage, Glucophage XR

Best time

With meals (XR with the evening meal)

07:00–09:00· With breakfast (immediate-release)
18:00–20:00· With evening meal

Taken with food to reduce stomach upset; once-daily XR is taken with dinner.

Strong evidence

Consistent clinical trials or official prescribing guidance support this timing.

Why this time works

Metformin lowers the liver's glucose output, which rises overnight and drives the 'dawn phenomenon'. Evening XR dosing targets this, and taking it with food greatly improves tolerability.

Body rhythm involved

Liver glucose output and insulin resistance rise in the early morning.

Other hormones & diabetes medicines

Levothyroxine

Synthroid, Euthyrox

On waking, empty stomach — or bedtime

Hormones & diabetesStrong evidence

Prednisolone / prednisone

Deltasone, Pred Forte (oral forms)

Morning

Hormones & diabetesStrong evidence

Hydrocortisone (replacement)

Cortef, Plenadren

Largest dose on waking, smaller early afternoon

Hormones & diabetesStrong evidence