Doctors still prescribe metformin, and it remains one of the most widely used diabetes medications in the world. What has changed is that metformin is no longer automatically the first drug every patient with type 2 diabetes receives. Updated treatment guidelines now encourage doctors to consider newer medications first for certain patients, particularly those with heart disease, heart failure, or kidney problems. This shift can create the impression that metformin has fallen out of favor, but the reality is more nuanced.
The Shift Away From “Metformin First”
For decades, metformin was the default starting medication for nearly everyone diagnosed with type 2 diabetes. The logic was straightforward: lower blood sugar first, deal with complications later. Treatment guidelines from every major medical organization listed metformin as step one.
That changed in a meaningful way starting around 2022 and 2023. The American Association of Clinical Endocrinology now recommends that doctors choose diabetes medications based on a patient’s full health picture, not just their blood sugar numbers. If someone has established or high-risk heart disease, heart failure, or chronic kidney disease, the guidelines say to prescribe a GLP-1 receptor agonist (like semaglutide) or an SGLT2 inhibitor (like empagliflozin) with proven benefits for those conditions, regardless of where blood sugar stands. Metformin doesn’t have the same evidence for protecting the heart and kidneys that these newer drug classes do.
This is a fundamental change in how doctors think about diabetes treatment. The old approach was glucose-centric: get the blood sugar down. The new approach is organ-protective: choose the drug that also shields the heart or kidneys. Since a large percentage of people with type 2 diabetes also have cardiovascular or kidney risks, many patients who would have started on metformin a few years ago now start on something else.
Newer Medications Offer Benefits Metformin Doesn’t
GLP-1 receptor agonists and SGLT2 inhibitors have demonstrated cardiovascular and kidney benefits in large clinical trials, which is the main reason they’ve moved ahead of metformin in certain situations. SGLT2 inhibitors, for instance, appear especially promising for younger patients. A nationwide cohort study published in the Journal of the American Heart Association found that in patients under 65 with low cardiovascular risk, SGLT2 inhibitors were associated with a 53% lower risk of death from any cause and a 78% lower risk of progressing to end-stage kidney disease compared to metformin. In patients over 65 or in the overall study population, the two drug classes performed similarly on cardiovascular outcomes.
Weight loss is another area where metformin has been eclipsed. Metformin produces modest weight loss in most people. The newer GLP-1 drugs produce substantially more. In the SURPASS-2 trial, patients already taking metformin who added semaglutide lost an average of 6.2 kg (about 14 pounds) over 40 weeks, while those who added tirzepatide at the highest dose lost 12.4 kg (about 27 pounds). That difference matters because weight loss itself improves blood sugar control, blood pressure, and cardiovascular risk.
Why Many Patients Still Take Metformin
Despite these advances, metformin has something the newer drugs don’t: affordability. A month’s supply of metformin costs between $4 and $15 without insurance. A month of semaglutide (Ozempic) without insurance runs $1,000 to $1,400. Even with insurance, semaglutide can cost $25 to $200 per month compared to roughly $4 for metformin. For millions of patients, especially those without robust insurance coverage, metformin remains the only realistic option.
Metformin also works. It effectively lowers blood sugar, has a decades-long safety record, and is well tolerated by most people who take it. For patients without significant heart or kidney disease, there’s no strong evidence that starting with a newer, more expensive drug produces better outcomes. The shift in guidelines applies most clearly to patients who already have or are at high risk for cardiovascular and kidney complications.
In practice, many patients take metformin alongside a newer medication. The SURPASS-2 trial, for example, studied tirzepatide and semaglutide as add-on therapies to metformin, not replacements for it. Metformin often serves as a low-cost foundation that other drugs build on.
The NDMA Contamination Scare
Some of the concern about metformin traces back to contamination issues that made headlines in 2020 and 2021. Several manufacturers voluntarily recalled batches of extended-release (ER) metformin after testing revealed levels of NDMA, a probable carcinogen, above acceptable limits. The FDA asked all companies making ER metformin to test every batch before releasing it to market.
Importantly, the FDA’s own testing found no NDMA contamination in immediate-release metformin, which is the most commonly prescribed form. The agency explicitly recommended that doctors continue prescribing metformin when clinically appropriate and warned patients not to stop taking it without a replacement. The recalls were limited to specific ER formulations from specific manufacturers, and no new recalls have been announced since early 2021. This issue is largely resolved, though it understandably made some patients and doctors uneasy.
Kidney Function Limits Who Can Take It
One real reason your doctor might stop or avoid prescribing metformin is declining kidney function. Metformin is processed by the kidneys, and when they aren’t working well enough, the drug can accumulate to dangerous levels.
Current guidelines from the Kidney Disease: Improving Global Outcomes (KDIGO) organization set clear thresholds. Metformin is considered safe when your estimated kidney filtration rate (eGFR) is above 45. Below 45, the dose should be reduced. Below 30, or in people on dialysis, metformin should be stopped entirely. Since kidney function naturally declines with age and diabetes itself damages the kidneys over time, many long-term diabetes patients eventually reach a point where metformin is no longer appropriate for them.
Side Effects That Drive People Away
Metformin is notorious for causing gastrointestinal problems, particularly diarrhea, nausea, bloating, and stomach cramps. These side effects are common enough that roughly 5% of patients stop taking the drug because of them. Starting at a low dose and increasing gradually helps, and the extended-release formulation tends to be gentler on the stomach, but for some people the discomfort never fully resolves.
Long-term use also carries a less well-known risk: vitamin B12 deficiency. Up to 10% of people taking metformin develop impaired B12 absorption, which can lead to deficiency over time. B12 deficiency causes fatigue, numbness or tingling in the hands and feet, and cognitive changes that can mimic other conditions. Regulatory bodies now recommend checking B12 levels in metformin users who show symptoms of deficiency or who have been on the drug long-term, but screening practices vary and the problem often goes unrecognized.
What This Means for You
If your doctor recently switched you from metformin to a newer medication, it likely reflects updated guidelines that prioritize heart and kidney protection, not a safety problem with metformin itself. If you’re newly diagnosed with type 2 diabetes and have cardiovascular or kidney risks, your doctor may skip metformin entirely and start with a GLP-1 or SGLT2 inhibitor. If you’re otherwise healthy and looking for affordable blood sugar control, metformin remains a solid, well-studied choice that most guidelines still endorse.
The short answer: doctors haven’t stopped prescribing metformin. They’ve stopped treating it as the only reasonable starting point.