Metformin
- Class: Biguanide
- Used for: type 2 diabetes
- Say it: met-FOR-min
- Forms: tablet, oral liquid
METFORMIN tells the liver to stop FORMING sugar — the tap at the source is turned down.
Its main action is reducing hepatic glucose production, not releasing insulin. That is exactly why it does not cause hypoglycaemia on its own.
It turns down the liver's glucose output rather than squeezing insulin out of the pancreas. That is why it almost never causes a hypo on its own, and why it is first-line.
The mechanism comic
One of five sample comics. The app has one for each of the 100 drugs.
Side effects
Common: diarrhea, nausea, metallic taste
Serious: lactic acidosis (rare), B12 deficiency
Typical dose
500 mg once or twice daily, up to 2 g daily
Titrate slowly with food to limit diarrhoea. Stop if eGFR falls below 30.
Check yourself
Why does Metformin rarely cause hypoglycaemia?
- It reduces the liver's glucose output rather than forcing insulin out
- It is simply a weak drug
- It blocks glucose absorption from the gut completely
- It is cleared from the body too quickly to cause one
Show answer
A. It reduces the liver's glucose output rather than forcing insulin out
A hypo needs insulin to be pushed out regardless of the glucose level. Metformin never does that — it lowers the supply side — so the floor is not driven down below normal.
See it, don't memorize it
The app has the mechanism comic and a patient case for Metformin – plus the name link, the class mnemonic, pronunciation you can hear, and a self-check, for the top 100 drugs. One purchase, no subscription, no account.