Metformin vs. Glipizide: What's the Difference?

All dosing amounts and timing are decisions for the person who writes the prescription, and they differ by formulation, kidney function and what else you take.

These are patterns a prescriber weighs, not rules you can apply to yourself. The same facts can point different ways depending on your other conditions.

If a person has a history of severe kidney problems, or of short-term or long-term metabolic acidosis including diabetic ketoacidosis, metformin is contraindicated, and a doctor may consider a different class altogether (GoodRx, 2025-10-13). Kidney function is why prescribers often recheck bloodwork before and during metformin treatment — the medicine is cleared by the kidneys.

If a person has a history of allergy to sulfonamide medications, or has Type 1 diabetes or diabetic ketoacidosis, glipizide is contraindicated (GoodRx, 2023-10-10). A sulfonamide reaction noted years ago is still worth repeating at every new appointment, because it may not have carried over into a current chart.

If a person is a child or young teenager with Type 2 diabetes, age limits the options: immediate-release metformin is approved for people 10 years of age and older, while glipizide is used to treat Type 2 diabetes in adults (GoodRx, 2025-10-13; GoodRx, 2023-10-10).

If a person has struggled with stomach upset on past medicines, or conversely with episodes of low blood sugar, a prescriber may weigh the two side effect profiles differently — the gut-related effects sit more with metformin, the low-blood-sugar risk more with glipizide. Practical factors also count: how many times a day you can realistically take a pill, what your insurance covers, and what a pharmacist quotes you at the counter.

It is not always one or the other. Glipizide and metformin are sometimes prescribed together, and a combination glipizide/metformin product exists (GoodRx, 2023-10-10).

Each item below is labelled with the drug or drugs it applies to. Report anything on this list to your prescriber or pharmacist rather than deciding what it means yourself.

• Diarrhea — both. Listed among common effects for metformin and reported in studies of extended-release glipizide (GoodRx, 2025-10-13; GoodRx, 2023-10-10).
• Gas — both. Common with metformin; passing gas was also reported with glipizide (GoodRx, 2025-10-13; GoodRx, 2023-10-10).
• Nausea or vomiting — metformin. Among the commonly reported effects, and part of why it is taken with food (GoodRx, 2025-10-13).
• Weakness — metformin. Reported as a common effect (GoodRx, 2025-10-13).
• Dizziness, nervousness and tremor — glipizide. Reported in clinical studies of the extended-release form (GoodRx, 2023-10-10).
• Low blood sugar — glipizide, and both together. Listed among common glipizide effects, and taking metformin alongside insulin or a sulfonylurea such as glipizide raises the risk of low blood sugar, which can be dangerous (GoodRx, 2023-10-10; GoodRx, 2025-10-13).
• Weight change — differs. Sulfonylureas including glipizide can cause weight gain; metformin is unlikely to cause weight gain, and some people lose a small amount (GoodRx, 2023-10-10; GoodRx, 2025-10-13).
• Lactic acidosis — metformin. Described as rare but potentially life-threatening (GoodRx, 2025-10-13).
• Dangerously low blood sugar — glipizide. The serious warning names hunger, fast heartbeat, shakiness, confusion and coma among its symptoms (GoodRx, 2023-10-10).

Call your doctor during office hours about ongoing diarrhea, nausea, gas, weakness, dizziness, tremor, nervousness, or weight change you did not expect, and about mild low-blood-sugar episodes you were able to treat yourself. These are things a prescriber can act on.

Seek emergency care now — call 911 or go to an emergency department for confusion, fainting or loss of consciousness, a seizure, shakiness with a fast heartbeat that does not improve after treating low blood sugar, or sudden unusual muscle pain, trouble breathing or severe weakness while taking metformin. Do not wait for a return call.