Lifestyle

Stomach Trouble or Unusual Tiredness on a Common Diabetes Pill Can Be Signs to Tell Your Doctor. What Older Adults Should Know

By Curtis Jones · November 5, 2026

Metformin is one of the medicines doctors most often prescribe for type 2 diabetes. MedlinePlus says it helps control blood sugar by lowering how much glucose you absorb from food and how much your liver makes, and by helping the body respond better to insulin. It does not cure diabetes, and it is not used for type 1 diabetes.

Most people who take it can stay on it for years. The points below are signs and precautions to talk over with a doctor, not reasons to stop the pill on your own. MedlinePlus is clear: continue taking metformin even if you feel well, and do not stop without talking to your doctor.

Common side effects that deserve a call if they are severe, lasting, come and go, or start late. MedlinePlus lists these for you to report:

Stomach and bowel trouble. Diarrhea, nausea, stomach discomfort, gas, indigestion, constipation or stomach pain.

Low energy. Lack of energy or weakness, along with headache, a change in taste, flushing, nail changes, muscle pain or rash.

A rare but serious warning sits at the top of the MedlinePlus page. Metformin may rarely cause lactic acidosis, a life-threatening buildup of lactic acid. The page says to tell your doctor if you have kidney disease, and that doctors may decide you should not take metformin. It also says to tell your doctor if you are over 65, or if you have had a heart attack, stroke, diabetic ketoacidosis, a coma, heart or liver disease, or a disease affecting the mitochondria.

Stop metformin and call the doctor right away, MedlinePlus says, if you have extreme tiredness, weakness or discomfort; nausea; vomiting; stomach pain; decreased appetite; deep and rapid breathing or shortness of breath; dizziness; lightheadedness; a fast or slow heartbeat; muscle pain; or feeling cold, especially in the hands or feet.

Other times the dose may need a pause. Tell the doctor before surgery, including dental surgery, or before an X-ray procedure that uses injected dye. MedlinePlus says you may need to stop metformin before the procedure and wait at least 48 hours before restarting, on the doctor’s schedule. Also tell the doctor about serious infection, severe diarrhea, vomiting or fever, or drinking much less fluid than usual, because you may need to stop until you recover.

Alcohol raises the risk. MedlinePlus warns that drinking alcohol increases the risk of lactic acidosis and may lower blood sugar, and says to ask how much is safe while on metformin.

Vitamin B12 comes up too. Before starting, tell the doctor if you have ever had low vitamin B12 levels. Keep lab appointments so kidney function and your response to the medicine can be checked.

If something feels off, write down when it started, how long it lasts and what else you take, then call the office that prescribed the medicine. Do not change the dose or quit on your own. Chest pain is also listed as a reason to call right away or get emergency care.

This article is for general information and is not medical advice. Do not stop or change any medicine without talking with the doctor who prescribed it. This article was produced with the assistance of AI and fact-checked against the sources cited by LightWave Reports.