What Is Metformin or Glucophage? (Benefits, Side Effects, Tips)


what is metformin

Do you have a prescription for, or are you taking Metformin (Glucophage)? Many patients of mine that have diabetes have never had diabetes education or proper instruction on diabetes medications. I share some basic take-aways that may benefit you just as they have my patients in the past. So lets start out with what Metformin is.

Metformin, also known as Glucophage (meaning, “glucose eater”), is the first line of treatment for people with type 2 diabetes, and some people with prediabetes. Metformin is in the biguanide category of glucose lowering medications. It can be prescribed as monotherapy or in conjunction with other meds, including insulin.

Metformin (Glucophage)

  • Oral medication
  • First line of treatment for type 2 diabetes, prediabetes, and PCOS (polycystic ovarian syndrome)
  • Well established anti-diabetic medication, introduced in the United States in 1995
  • Cardiovascular benefits were identified by the UKPDS (United Kingdom Prospective Diabetes Study) in 1998.
  • Primarily decreases hepatic (liver) glucose (Sugar) production
  • Decreases glucose absorption in the gut
  • Improves insulin sensitivity
  • Other US brand names for Metformin include Glucophage IR (Immediate release) Glucophage XR (extended release), Fortamet, Glumetza, and Riomet (liquid form)

For additional historical information on Metformin see Metformin: Historical Overview a Pub Med article by the National Library of Medicine.

What is the dose for Metformin (Glucophage)?

Metformin IR (immediate release) or Glucophage comes in 500 mg, 850 mg, and 1000 mg oral tablets used to treat blood sugars in people with diabetes. The max daily dose is 2500 mg.

Metformin ER (extended release) or Glucophage XR, lasts longer than immediate release Metformin, has fewer side effects, and can be taken once daily. The max daily dose of Glucophage XR is 2000 mg.

Metformin 850 mg is Metformin hydrochloride. The 850 mg Metformin hydrochloride is equivalent to 663 mg Metformin (medicines.org). It is a film-coated tablet. It tends to be used in overweight people with diabetes.

Riomet ER is the liquid form of Metformin. It is dosed once daily, and is appropriate for those who have problems swallowing.

Benefits of Metformin 

  • A1c reduction of 1.5 – 2%
  • Neutral effect on weight, or some weight loss
  • Works on the overnight fasting regulation of blood sugars
  • Low risk of hypoglycemia (low blood sugar) unless combined with insulin or other blood glucose lowering agents 
  • Anti-cancer, anti-heart disease, anti-Alzheimer’s (Source)
  • Inexpensive drug

Side effects of Metformin 

  • Nausea and vomiting
  • Diarrhea
  • Flatulence 
  • Heartburn
  • Abdominal pain and bloating
  • Vitamin B12 deficiency/anemia – possible fatigue
  • Unpleasant “metal” taste in your mouth
  • Lactic acidosis (Source)

Caution use of Metformin with:

  • Renal (kidney) disfunction
  • CHF (congestive heart failure) requiring treatment
  • Hepatic (liver) disease
  • Excessive alcohol use

Why am I Seeing Metformin in my Stools? Is it Being Absorbed?

I have had three patients report to me that they see their Metformin in their stools. My patients questioned whether the Metformin is being absorbed. 

I have collaborated with Dr. Robert Sjoberg (now retired) and Dr. Derrick Aipoalani (“Dr. A”) from St. Luke’s Endocrinology about this topic. Both reported that the medication is being absorbed and it is the casing of their medication that they are seeing in their stools. 

Does Metformin or Glucophage Make My Stool Darker in Color?

Usually, there is no cause for concern if stools are dark. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) report that bleeding in the GI (gastrointestinal) tract can cause black, tarry stools.

According to Mayoclinic.org, the incidence of black stools and dark urine are unknown.

If you see bright red blood in your stool, or you are experiencing unusual discomfort, seek medical attention.

Food plays a role in the color of stool. Black icing on cakes and dark cookies can cause stool to turn black.

Some medications or over-the-counter drugs will darken stools, such as iron pills.

Rectal bleeding can occur with more serious conditions, such as UC (ulcerative colitis), so if you have concerns, contact your medical provider.

When is Metformin Usually Prescribed for People with Type 2 Diabetes?

Metformin or Glucophage can be used in combination with another glucose-lowering agent with an A1c of 9% or less.

As a general rule, Metformin is prescribed when diet and exercise alone are not enough to control blood sugars. It is also prescribed in the pre-diabetic population, as well, to help prevent type 2 diabetes. Metformin is recommended if A1c is less than or equal to 7.5%, according to the most recent AACE/ACE (American Association of Clinical Endocrinology/American College of Endocrinology) algorithm.

Is There A Good Substitute For Metformin?

Never stop any of your medications, including Metformin, without discussing it with your primary care provider or your endocrinologist.

If you are looking into switching medications I wrote a detailed article on alternatives to Metformin that you can read in depth on metformin alternatives.

Before you decide to switch medication, I would like to point out some details on Metformin. I have met many patients that have had little or no diabetes education, including limited education and training about their diabetes medications.

Am I taking my Metformin correctly?

  • The maximum daily dose of Glucophage is 2500 mg, and 2000 mg daily for Glucophage XR.
  • When starting Metformin or Glucophage, I recommend starting at 500 mg once daily. Do this for one week, then increase your dose to 500 mg with your morning and evening meal.
  • If you are experiencing unpleasant side effects after one week, continue the once daily dose for another week before adding the second dose.
  • Add 500 mg with supper so you are taking 500 mg with breakfast and supper for one week.
  • When you have completed your week of taking 500 mg of Metformin with breakfast and supper, increase your dose to 1000 mg at breakfast and 500 mg at supper. Practice this for one week before taking the 1000 mg, twice daily.
  • Note that some physicians will prescribe Metformin, three times daily. It will be the decision of your provider. 
  • If someone is experiencing excessive side effects or discomfort, they are often switched to the extended release formula.
  • Always take this medication WITH A MEAL, or WITH FOOD. It significantly reduces your chances of ill side effects if you do this.
  • If you have additional questions after talking with your doctor, your pharmacist is a good resource, as well. 
  • Are you taking a smaller dose? See my article on, “Can I cut my Metformin in half?”

Final Comments

If you have questions or concerns about your diabetes medications, schedule an appointment with your primary care provider or your certified diabetes care and education specialist. This appointment is covered by most insurances. 

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