Can You Cut Or Split Metformin ER In Half?

In our latest question and answer, the pharmacist discusses whether or not metformin ER tablets can be cut or split in half.


My doctor said to cut in half my 500 mg metformin ER tablet to lower my dose. Will this damage the metformin 500 mg ER tablet?

Asked by East Side On Nov 07, 2022

Answered by
Medical Content Reviewed By HelloPharmacist Staff

Published Nov 07, 2022
Last updated May 23, 2024

Key points

  • There are several metformin extended-release drugs available, Glucophage XR, Glumetza ER, and Fortamet ER. They are all available generically.
  • All metformin ER drugs should not be cut, split, or crushed. Doing so will destroy the extended-release mechanism of the drug.


You are correct that extended-release metformin products should not be cut, split, or crushed as these actions will ruin the extended-release properties of the drug. Only immediate-release metformin tablets can be split.

There are actually 3 different extended-release metformin products available, and they all cannot be altered. They are:

  • Glucophage XR
  • Glumetza ER
  • Fortamet ER

Why You Can't Cut Or Split Metformin ER

As mentioned, you cannot cut, split, crush or otherwise alter metformin ER tablets. Doing so will destroy the extended-release properties of the drug, releasing the entire dose at once and potentially increasing the risk of side effects, namely, gastrointestinal side effects.

The 3 extended-release metformin products have a different extended-release mechanisms, but the general principle behind them is the same:

  • Glucophage XR: Glucophage XR uses a 'dual hydrophilic polymer system'. When a Glucophage XR tablet is taken by mouth, the polymer layer swells when it comes into contact with saliva/gastric contents. The polymer layer forms a gel on the surface of the tablet and the drug is then released by diffusion through the gel layer.

  • Glumetza: Glumetza tablets use an extended-release mechanism known as 'gastro-retentive' technology. The tablets are designed to remain ('float') in the stomach and will deliver metformin to the upper GI tract over an extended period of time.

  • Fortamet: ​Fortamet tablets use single-composition osmotic technology (SCOT). Once exposed to the contents of the stomach and GI tract, water is taken up through the tablet membrane, which dissolves the drug located in the center of the tablet. The drug then slowly exits through a small hole in the tablet. Tablets that use osmotic technology often leave a "ghost tablet" in the stool.

Altering any extended-release metformin product will destroy the extended-release properties of the drug, potentially increasing the risk of side effects and decreasing how well it controls your blood sugar.

You should discuss with your doctor how they want you to lower your dose. The instruction you described (to cut the tablet) may have been simply a mistake by whoever told you to do that. In addition, there may be some confusion regarding the drug and dosage form you are taking.

Metformin is available as 500 mg in both an immediate-release version and an extended-release version. Only the immediate-release version can be cut or split safely. Perhaps they wanted to switch you to the immediate release version and have you split that.

Alternatives To Splitting Metformin ER

Metformin ER and immediate-release metformin are available in multiple strengths. If you need to adjust the dosage of your extended-release version, talk to your doctor about getting a different strength. It is available as:

  • Metformin ER 500mg
  • Metformin ER 750mg
  • Metformin ER 1,000mg

Final Words

I hope you found this helpful! Thank you for reaching out.


  • Fortamet Prescribing Information, AccessFDA
  • Gastro-retentive drug delivery systems and their in vivo success: A recent update, ScienceDirect
  • Glumetza Prescribing Information, AccessFDA
  • The Role of Oral Controlled Release Matrix Tablets in Drug Delivery Systems, PubMrf

About the Pharmacist

Dr. Brian Staiger, PharmD

Dr. Brian has been practicing pharmacy for over 13 years and has wide-ranging experiences in many different areas of the profession. From retail, clinical, program development, and administrative responsibilities, he's your knowledgeable and go-to source for all your pharmacy and medication-related questions! Dr. Brian Staiger also has herbalist training and educational certificates in the field of medical ethnobotany. Feel free to send him an email at [email protected]! You can also connect with Dr. Brian Staiger on LinkedIn.

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