What is metformin used for?

Metformin is used as an addition to diet and exercise to help control blood sugar in adults with type 2 diabetes.

Can I crush or chew metformin extended-release tablets?

No, you must swallow metformin extended-release tablets whole and never crush, cut, or chew them.

What are the symptoms of lactic acidosis from metformin?

Symptoms can include muscle pain, stomach pain, feeling weak or tired, breathing difficulties, and feeling cold.

Does metformin cause weight loss or vitamin issues?

Metformin may lower your vitamin B12 levels, so your doctor may want to check these levels every 2 to 3 years.

Can I take metformin if I have kidney problems?

Metformin should not be used if you have severe kidney impairment (an eGFR below 30).

What happens if I take too much metformin?

Taking too much can lead to low blood sugar or a dangerous buildup of lactic acid in your blood.

Is metformin safe to take during pregnancy?

There is not enough data to fully determine the risk of major birth defects, but poorly controlled diabetes itself can be risky during pregnancy.

What are common side effects of metformin?

Common side effects include diarrhea, nausea, stomach pain, gas, and headaches.

Metformin | CAS 657-24-9 | XZWYZXLIPXDOLR

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Anti-diabetic

Metformin is a medication used to help manage blood sugar levels in adults with type 2 diabetes. It is typically used alongside a healthy diet and regular exercise to improve glycemic control.

How it worksMetformin is a biguanide that helps improve how your body handles blood sugar.

Brand names:Metformin

Used for

Type 2 diabetes mellitus

Conditions

Type 2 diabetes mellitus

Class

BiguanideAntidiabeticAnti-diabeticEndocrine

How to take

FormsExtended-release tablets

RoutesOral

The usual starting dose is 500 mg once daily with your evening meal. Your doctor may increase this weekly by 500 mg increments, up to a maximum of 2,000 mg once daily.

Swallow the tablets whole. Do not crush, cut, or chew them.

Key warnings

Metformin carries a boxed warning for lactic acidosis, a rare but life-threatening buildup of lactic acid in the blood. Symptoms can include muscle pain, stomach pain, breathing problems, and feeling very tired or cold. Risk factors include kidney problems, excessive alcohol use, and certain medical procedures.

·Metformin carries a boxed warning for lactic acidosis, a rare but life-threatening buildup of lactic acid in the blood. Symptoms can include muscle pain, stomach pain, breathing problems, and feeling very tired or cold. Risk factors include kidney problems, excessive alcohol use, and certain medical procedures.
·Risk of lactic acidosis
·Risk of Vitamin B12 deficiency
·Risk of low blood sugar when used with insulin

Do not use if

·Severe kidney impairment (eGFR below 30 mL/min/1.73 m2)
·Allergy to metformin
·Acute or chronic metabolic acidosis, including diabetic ketoacidosis

Side effects

Common

DiarrheaNausea or vomitingAbdominal painConstipationStomach swellingHeartburnGasDizzinessHeadacheUpper respiratory infectionTaste changes

Serious

·Lactic acidosis (a serious condition that can be fatal)
·Vitamin B12 deficiency
·Low blood sugar (hypoglycemia), especially if taken with insulin

Seek help if

·Unexplained hyperventilation
·Muscle pain
·Malaise
·Unusual sleepiness
·Abdominal pain

Interactions

·Carbonic anhydrase inhibitors (may increase lactic acidosis risk)
·Drugs that reduce metformin clearance like ranolazine, vandetanib, dolutegravir, and cimetidine
·Alcohol (can increase the risk of lactic acidosis)

FoodIt is recommended to take metformin with your evening meal.

AlcoholAvoid excessive alcohol intake while taking metformin, as it can increase the risk of lactic acidosis.

Special populations

PregnancyThere is limited data regarding the safety of metformin in pregnant women. While some studies have not shown a clear link to major birth defects, poorly controlled diabetes during pregnancy can pose risks to both mother and baby.

PediatricThe safety and effectiveness of metformin extended-release tablets have not been established in children.

GeriatricDoctors should use caution when prescribing metformin to older adults, as they may be at a higher risk for lactic acidosis and are more likely to have decreased kidney or liver function.

Talk to your doctor

Monitor

·Renal function (eGFR)
·Vitamin B12 levels
·Blood lactate levels

Questions to ask

·What is my current eGFR and is it safe for metformin?
·Should I monitor my Vitamin B12 levels regularly?
·How will my insulin dose change if I start metformin?
·What should I do if I experience muscle pain or unusual tiredness?

Pharmacokinetics

ExcretionMetformin is dialyzable with a clearance of up to 170 mL/min under good hemodynamic conditions.

Practical

OverdoseAn overdose of metformin can lead to low blood sugar or lactic acidosis. In cases of suspected overdose, medical professionals may use hemodialysis to help remove the drug from the body.

Educational summary derived from FDA labeling, AI-assisted. Not medical advice — consult a healthcare professional. Updated 2026-04-26.