Key takeaways:
The main difference between modified-release (MOD) and osmotic-release (OSM) metformin is the way the medication is slowly released in the body.
Since MOD metformin (Glumetza) and OSM metformin (Fortamet) work slightly differently, one can’t be automatically used in place of the other.
Glumetza is taken once a day. Fortamet is usually taken once a day, but some people may need to take it twice a day. Glumetza and Fortamet both have a maximum dosage of 2,000 mg per day.
Glumetza and Fortamet are available as lower-cost generics. GoodRx can help you save over 95% off the average retail price at certain pharmacies.
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Metformin is commonly used to treat Type 2 diabetes in combination with a diabetes-friendly diet and regular exercise. In general, metformin is available in immediate-release (IR) and extended-release (ER) dosage forms. And within the ER version, there are two types: MOD and OSM metformin.
Compared with IR tablets, both ER tablets can be taken less frequently. This is because they slowly release metformin throughout the day. The digestive side effects of ER metformin may also be easier for some people to tolerate.
But what do MOD and OSM stand for? Let’s take a closer look at the differences between these ER metformin medications, including what these abbreviations mean, how they work, and whether they can be used interchangeably.
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Note: The brand names for MOD metformin (Glumetza) and OSM metformin (Fortamet) have been discontinued from the U.S. market. But for ease of reading, this article uses those brand names when discussing the two formulations.
What does MOD stand for?
MOD stands for “modified release.” Glumetza is the former brand name for MOD metformin. The tablets are specially formulated to control how fast the tablet breaks down in your body. They contain a substance that allows the metformin tablet to stay in your stomach longer than IR metformin does.
While in the stomach, the tablet absorbs gastric juices (stomach fluid or acid) and swells. As the tablet becomes larger in size, medication is released slowly from the pill. It takes about 7 to 8 hours after taking Glumetza for the medication to reach its highest levels in your body.
What does OSM stand for?
OSM stands for “osmotic release.” Fortamet is the former brand name for OSM metformin. Its tablets use a single-composition osmotic technology delivery system. This delivery system helps control the release of metformin by using a special core that’s surrounded by a semipermeable layer. This means that the layer allows only certain substances to move through it.
Like Glumetza, Fortamet’s tablets allow metformin to remain in your stomach longer than the IR dosage form. The medication is slowly released and reaches its highest levels about 6 hours after taking it.
Do Glumetza and Fortamet have generic versions?
Yes, Glumetza and Fortamet have generic versions available. The first generic versions of Glumetza and Fortamet came to the U.S. market in 2016. In the years since, other manufacturers have also launched generic versions of Glumetza.
These generic medications went through extensive FDA testing to make sure they work similarly to each of the brand-name medications. They’ve helped lower medication costs over time without sacrificing quality.
What are the typical dosages of Glumetza and Fortamet?
In most cases, people take Glumetza and Fortamet once daily with their evening meal. But some people may need to take Fortamet twice a day.
Glumetza and Fortamet come as 500 mg and 1,000 mg ER tablets. The typical starting dosage for either medication is 500 mg per day with your evening meal. Your prescriber will adjust your daily dosage over time based on how you tolerate and respond to the medication.
The maximum dosage for Glumetza and Fortamet is 2,000 mg per day, usually taken once daily. But your prescriber may recommend taking Fortamet 1,000 mg twice daily if you haven’t reached your blood glucose (sugar) goals with 2,000 mg once daily.
Can Fortamet and Glumetza be used in place of one another?
Fortamet and Glumetza are not interchangeable. That’s because the tablets release metformin in your body in different ways. So the FDA doesn’t consider these two products to be equivalent. But there are generic versions of metformin ER that are interchangeable with Fortamet and Glumetza.
Good to know: There’s a third metformin ER product available (former brand-name Glucophage XR). This medication isn’t interchangeable with Fortamet or Glumetza either.
How to save on Glumetza and Fortamet
There are ways to save on the generic versions of Glumetza and Fortamet.
Save with GoodRx. GoodRx can help you save over 95% off the average retail price of the generic versions. The price of 30 generic Glumetza 1,000 mg tablets at certain pharmacies is as low as $24.07 with a free GoodRx discount. The price of 30 generic Fortamet 1,000 mg tablets may be as little as $22.80 at certain pharmacies.
Save with Companion. You can access discounted prescription medications with a GoodRx Companion subscription. Over 250 medications are available for free, with hundreds more for under $10. The program also includes benefits to help you cut your self-pay costs, such as lower prices for online care visits, discounts on dental care, and other health services.
Frequently asked questions
No, there isn’t a natural form of metformin that’s FDA approved to help manage Type 2 diabetes. There may be vitamins or supplements that can be useful if you’re living with the condition. But they should be added to your other diabetes medications and lifestyle changes (not used in place of). And you should take these products only if a healthcare professional tells you to. Certain vitamins and supplements interact with other diabetes medications, including metformin.
Metformin is safe and works well for many people with Type 2 diabetes. But if you can’t take it, there are other oral and injectable medications to consider. Your prescriber can help you find an option that’s safe for you.
Metformin alternatives include:
Glucagon-like peptide-1 (GLP-1) receptor agonists, such as Ozempic (semaglutide)
Glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonists, such as Mounjaro (tirzepatide)
Sodium-glucose cotransporter-2 (SGLT2) inhibitors, such as Jardiance (empagliflozin)
It’s possible for some people to manage diabetes without metformin. Good tips to follow that can help balance your blood sugar include:
Increasing the amount of protein in your diet
Slowly adding more fiber to your routine
Using sugar substitutes, such as stevia, instead of white sugar
Exercising or adding more movement to your routine (especially right after meals)
Getting enough sleep at night
Performing activities that can help lower your stress levels, such as deep breathing
Talk with your diabetes care team about the best options to help manage your diabetes.
No, there isn’t a natural form of metformin that’s FDA approved to help manage Type 2 diabetes. There may be vitamins or supplements that can be useful if you’re living with the condition. But they should be added to your other diabetes medications and lifestyle changes (not used in place of). And you should take these products only if a healthcare professional tells you to. Certain vitamins and supplements interact with other diabetes medications, including metformin.
Metformin is safe and works well for many people with Type 2 diabetes. But if you can’t take it, there are other oral and injectable medications to consider. Your prescriber can help you find an option that’s safe for you.
Metformin alternatives include:
Glucagon-like peptide-1 (GLP-1) receptor agonists, such as Ozempic (semaglutide)
Glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonists, such as Mounjaro (tirzepatide)
Sodium-glucose cotransporter-2 (SGLT2) inhibitors, such as Jardiance (empagliflozin)
It’s possible for some people to manage diabetes without metformin. Good tips to follow that can help balance your blood sugar include:
Increasing the amount of protein in your diet
Slowly adding more fiber to your routine
Using sugar substitutes, such as stevia, instead of white sugar
Exercising or adding more movement to your routine (especially right after meals)
Getting enough sleep at night
Performing activities that can help lower your stress levels, such as deep breathing
Talk with your diabetes care team about the best options to help manage your diabetes.
The bottom line
Metformin has a few different extended-release (ER) products, including Glumetza and Fortamet. They’re different in how they slowly release metformin in your body over time. Since they don’t work exactly the same way, Glumetza and Fortamet aren’t interchangeable.
Glumetza is taken once a day. Fortamet is usually taken once a day, but some people may need to take it twice a day. Glumetza and Fortamet both have a maximum dose of 2,000 mg per day.
Ask your prescriber whether Glumetza or Fortamet would be right for you.
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References
American Diabetes Association Professional Practice Committee for Diabetes. (2026). 5. Facilitating positive health behaviors and well-being to improve health outcomes: Standards of care in diabetes—2026. Diabetes Care.
American Diabetes Association Professional Practice Committee for Diabetes. (2026). 9. Pharmacologic approaches to glycemic treatment: Standards of care in diabetes—2026. Diabetes Care.
Glenmark Pharmaceuticals. (2019). Glenmark Pharmaceuticals receives ANDA approval for metformin hydrochloride extended release tablets USP, 500 mg and 1000 mg.
Lupin. (2016). Lupin launches generic Glumetza HCL ER tablets in the US.
Mylan. (2016). Mylan launches generic Fortamet tablets.
Mylan Pharmaceuticals. (2026). Metformin hydrochloride- metformin tablet, film coated, extended release [package insert].
Santarus. (2019). Glumetza- metformin hydrochloride tablet, film coated, extended release [package insert].
Ysern, X. (2003). NDA 21-574. Fortamet extended-release tablets. Metformin HCL, USP ER tablets. Andrx Labs.
Ysern, X. (2004). NDA 21-748. Glumetza: metformin hydrochloride extended release tablets. Biovail Laboratories.
