“I don’t want metformin”
When my patients get diagnosed with diabetes, the first medication I want to prescribe is metformin. Almost immediately, many push back, saying metformin is “a terrible medication” and, “isn’t there something else they can try first?”
I always wondered why there was so much resistance to trying metformin among my Black patients.
Metformin side effects are common
Metformin is the most prescribed diabetes medicine in the world. It is inexpensive, it does not cause weight gain or low blood sugar on its own, and it has decades of safety data. But up to 1 in 4 people who take it have stomach side effects: nausea, gas, bloating, and diarrhea, which can be explosive at times. In a small 2023 study of Black adults with diabetes, about a third had stopped metformin because of side effects, and another third were still having symptoms while taking it.
Insurance companies frequently “insist” that clinicians prescribe metformin first, as an inexpensive option that generally works well for diabetes. That makes getting metformin right even more important.
Why is metformin hard on the stomach?
Metformin works partly in the gut, and the amount that builds up in the intestine affects how well people tolerate it. Studies suggest that genes play a role, especially SLC22A1, which makes a transporter called OCT1 that moves metformin from the gut into the liver. Researchers are also studying differences in gut bacteria between people who tolerate metformin and people who do not.
The precision medicine connection
Too many doctors treat metformin as one-size-fits-all. Precision medicine shows four reasons Black patients deserve a more careful approach.
1. Metformin may work better for African Americans
In a study of nearly 20,000 patients at Henry Ford Health System in Detroit, metformin lowered A1c by about 0.9 points in African Americans, compared with 0.42 points in White patients, more than twice the benefit (Journal of Clinical Endocrinology & Metabolism, 2014). That makes it worth the effort to find a way to tolerate it.
2. The genes behind intolerance are still being mapped in Black patients
The OCT1 gene variants linked to metformin stomach problems were identified mostly in people of European ancestry, and several are less common in people of African ancestry. That means the explanation for intolerance in Black patients may lie elsewhere, including the gut microbiome. Genetic testing for metformin is not routine yet, but this is an active area of research and another reason Black patients need to be included in diabetes studies.
3. Your kidney numbers may have changed
Metformin dosing depends on kidney function (eGFR). In 2021, labs stopped using a “race adjustment” that had made Black patients’ kidney function look better than it was. Under the new race-free equation, about 28% of Black patients in moderate kidney disease (stage 3a) moved to a lower stage where the metformin dose should be reviewed (Clinical Chemistry, 2023). If you have been on metformin for years, ask your doctor whether your dose still fits your current eGFR.
4. Check your vitamin B12
Long-term metformin use can lower vitamin B12. Low B12 causes numbness and tingling in the feet that is easy to mistake for diabetic nerve damage, along with fatigue and anemia. The American Diabetes Association recommends checking B12 periodically in people taking metformin, especially if nerve symptoms appear.
These are the kinds of differences covered in Better Black Health, written for patients and families, and Precision Medicine for African Americans (Springer Nature), written for clinicians.
Use a slower and more deliberate pace
Most people can tolerate metformin with the right approach:
- Start low: often 500 mg once a day, increasing slowly over several weeks.
- Take it with meals: usually with the evening meal at first.
- Ask about extended-release (ER) metformin: it is often much easier on the stomach.
- Don’t stop on your own: tell your doctor about side effects so the dose or form can be adjusted. If metformin still does not work for you, there are other good options.
Patient education on medication adherence is crucial because it empowers individuals to manage their condition effectively and understand the importance of consistent medication use. By educating patients about potential side effects and how to mitigate them, clinicians can improve adherence and ensure better health outcomes. Additionally, informed patients are more likely to communicate openly about their experiences, allowing for timely adjustments to their treatment plan.
Tools that help you stay on track
Implementing a medication tracking app can help patients monitor their adherence and remind them to take their medication on schedule. Another effective method is using a pill organizer with daily compartments to keep track of doses taken. Regular follow-up appointments or check-ins with healthcare providers can also ensure that any issues with adherence are promptly addressed.
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