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Extended-Release Metformin: What’s the Difference Between MOD and OSM?

Ross Phan, PharmD, BCACP, BCGP, BCPSAlyssa Billingsley, PharmD
Updated on July 27, 2022

Key takeaways:

  • The 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.

  • While Glumetza and Fortamet aren’t interchangeable, both are effective at treating Type 2 diabetes along with a healthy diet and exercise routine.

Metformin tablets spilling out of a plastic bag.
girubalani garnarajan/iStock via Getty Images

Metformin is commonly used to treat Type 2 diabetes in combination with diet and exercise. In general, metformin is available in regular immediate-release (IR) and extended-release (ER) dosage forms. And within the ER version, there are two different types: MOD and OSM metformin.

Compared to IR tablets, both ER tablets can be taken less frequently due to their slow release of metformin throughout the day. ER metformin may be easier on the stomach, which is helpful if you need to take the medication long-term. 

You might be wondering, “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 in place of one another. 

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What does MOD stand for?

MOD stands for modified release. Glumetza is the MOD metformin product, and it uses advanced delivery systems known as AcuForm® (for the 500 mg tablet) and Smartcoat® (for the 1000 mg tablet). These delivery systems contain a substance that allows the metformin tablet to stay in the stomach for an extended period of time. 

While in the stomach, the tablet absorbs gastric juices (stomach fluid or acid) and swells. As the tablet becomes larger in size, medication is slowly released over a time span of 8 to 9 hours

Does Glumetza have a generic?

Yes, Glumetza does have generic versions. In fact, generic Glumetza products have been available for years. In 2019, the FDA also approved another generic Glumetza product, made by the Glenmark manufacturer. 

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What is the maximum dose and available strengths of Glumetza?

Glumetza comes in 500 mg and 1,000 mg ER tablets. The typical starting dosage is 500 mg per day. And the maximum dose is 2,000 mg per day, which is taken once daily. Your healthcare provider will adjust your daily dosage over time based on how you tolerate and respond to the medication.

What does OSM stand for?

OSM stands for osmotic release. Fortamet is the OSM metformin product. Its tablets use a single-composition osmotic technology (SCOT) delivery system. This delivery system helps control the release of metformin by using a special core that’s surrounded by a semipermeable layer, or a layer that only allows certain substances to move through it. 

Does Fortamet have a generic?

Yes it does. Similar to Glumetza, Fortamet also has had generic versions available for years. For example, the Mylan manufacturer launched a generic Fortamet product in 2016

What is the maximum dose and available strengths of Fortamet ?

Similar to Glumetza, Fortamet’s maximum dose is 2,000 mg per day, which you can take once daily. But your healthcare provider may recommend giving 1000 mg twice daily a try if you haven’t reached your blood sugar goals with 2,000 mg once daily. 

Brand-name Fortamet used to come in 500 mg and 1000 mg ER tablets. Now, it’s only available in 1,000 mg ER tablets. However, generic 500 mg ER tablets are still available.

Metformin modified vs. osmotic release

One ER metformin version isn’t better than the other. 

Both metformin modified (Glumetza) and metformin osmotic (Fortamet) are approved to treat Type 2 diabetes, along with a healthy diet and regular exercise. In general, metformin has been shown to lower the risk for diabetes-related complications, such as cardiovascular events (e.g., heart attack). 

So, choosing one over may come down to insurance coverage and your preferences. 

Can Fortamet and Glumetza be used in place of one another?

Fortamet and Glumetza are not interchangeable. That’s because the FDA doesn’t consider these two products to be therapeutically equivalent. However, there are generic versions of ER metformin that are interchangeable with Fortamet. And the same goes for Glumetza.

The bottom line

Metformin has a few different ER products, including Glumetza and Fortamet. They’re different in how they slowly release metformin over time. Since they don’t work exactly the same way, Glumetza and Fortamet aren’t interchangeable. But both ER products are effective treatment options for Type 2 diabetes when used with a healthy diet and regular exercise.

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Why trust our experts?

Ross Phan, PharmD, BCACP, BCGP, BCPS
Ross Phan is a board-certified clinical pharmacist. She has roughly two decades of healthcare experience — with most of her experience being pharmacy related.
Samvida Patel, MNSP, INHC
Samvida Patel, MNSP, INHC, is a health editor at GoodRx. She is a nutritionist and integrative nutrition health coach with over 8 years of experience in health communications.
Alyssa Billingsley, PharmD
Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.
View All References (9)

Han, Y., et al. (2019). Effect of metformin on all-cause and cardiovascular mortality in patients with coronary artery diseases: A systematic review and an updated meta-analysis. Cardiovascular Diabetology.

Holmberg, M., et al. (2004). RxProduct news profile: Fortamet ER (metformin hydrochloride). Pharmacy Times.

Santarus, Inc. (2019). Glumetza [package insert].

Shionogi Inc. (2021). Fortamet [package insert].

U.S Pharmacist. (2011). Glumetza (metformin HCL extended-release tablets): Initial therapy in adult patients with type 2 diabetes. Product Information Guide.

U.S. Food and Drug Administration. (2022). Orange Book: Approved drug products with therapeutic equivalence evaluations.

U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs.

U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs.

Vermes, K. (2016). Mylan launches generic version of Fortamet. Pharmacy Times.

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

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