How does Metformin work?

In Type 2 Diabetes, one of the reasons blood sugars can be high (especially in the morning time) is because the liver makes too much sugar. It is “insulin resistant”, meaning it doesn’t get “shut off” from insulin’s signal.

This can be why, even if you haven’t eaten any food, sugars can increase steadily overnight - as the liver makes sugar.

The job of Metformin is to tell the liver NOT to make extra sugar – so it can be especially helpful for lowering high fasting blood sugars.


Metformin: The Good

  • It is inexpensive - regardless of insurance! Most drug stores have this on their $4 generic drug list.
  • It can help with weight loss. While most people do not lose a substantial amount of weight with Metformin, often patients can lose a few pounds after taking it over a few months.
  • When taken alone, it does not cause low blood sugars. Since it does not increase insulin levels, metformin alone doesn’t cause low blood sugars (hypoglycemia). Other prescription medications like glimepiride and glipizide (or insulin itself) can cause low sugars because they tell the pancreas to make more insulin.


Metformin: The Bad

  • Diarrhea is the most common complaint from Metformin. It can help to take an extended-release version and to start with a very low dose (250-500 mg).
  • Metformin can reduce the absorption of Vitamin B12 from food – resulting in Vitamin B12 deficiency, which can cause or worsen nerve pain and make you feel tired. The risk of low B12 levels goes up the longer you take Metformin. So, it can be important to take a Vitamin B12 supplement along with Metformin to prevent this.



Metformin hurts the kidneys!

Metformin does NOT cause kidney damage, but your doctor will monitor your kidney function while you take Metformin. This is because Metformin is cleared from the body by the kidneys… and if the kidneys aren’t working well – the Metformin levels can build up and cause issues. One of the very rare but life-threatening safety concerns with this is lactic acidosis. Because of this, if your kidney function starts to decline to a certain point (which is common in Type 2 Diabetes) – Metformin will be stopped.

Remember, the best way to protect the kidneys is by controlling blood sugars. If Metformin is helping to control sugar levels, then it is actually beneficial for the kidneys.


Metformin causes cancer!

Actually – it is just the opposite! A majority of clinical studies show that Metformin has a protective effect against cancer (including breast and colon cancer). People with Type 2 diabetes are at increased risk of cancers in general – possibly from insulin resistance. However,  studies show as much as a 27% reduced risk of developing colon cancer for people who take Metformin.

Some research study links to support this: