I recently looked back at my diabetes medicines and noticed something I had almost stopped thinking about. Metformin had been part of my treatment for years.
The brand name and dose had changed. Doctors had adjusted the treatment as my needs changed. Yet metformin remained somewhere in the prescription.
That made me ask a simple question: when someone has taken metformin for several years, what should they actually discuss with their doctor?
The answer involves more than blood sugar. Long-term treatment deserves a periodic review of kidney function and vitamin B12. Persistent stomach or bowel problems also deserve attention. If another diabetes medicine such as empagliflozin has been added, the conversation becomes broader still.
This is not a reason to stop metformin. It is a reason to have a better conversation with the doctor who prescribes it.
My Own Experience Raised the Question
I started taking a metformin-containing diabetes medicine in 2019. Over time, doctors changed my treatment.
At one stage, I was prescribed metformin 1000 mg. Bowel problems later became an issue, and another physician switched me to sustained-release metformin 750 mg.
The change made me think about something many patients probably experience. We tend to remember our latest prescription. We do not always think about the total number of years we have been exposed to a medicine.
For metformin, that history matters.
The American Diabetes Association’s 2026 Standards of Care say that metformin remains a useful glucose-lowering treatment for older adults because it has a low risk of causing hypoglycaemia when used by itself. But the ADA also stresses that its use needs regular reassessment.
For people taking metformin for more than four years, the ADA recommends annual monitoring of vitamin B12 levels. That is a small detail with potentially important consequences.
Ask About Vitamin B12
Metformin can interfere with vitamin B12 status during long-term treatment. The problem may develop quietly. A person may take metformin for years without connecting a new symptom with B12 deficiency.
Possible B12 deficiency symptoms can include unusual tiredness, weakness, numbness or tingling. Anemia may also occur.
For somebody with diabetes, numbness and tingling present an additional problem. It is easy to assume that every strange sensation in the feet comes from diabetic neuropathy. Sometimes another explanation needs investigation.
The 2026 ADA guidance recommends considering periodic B12 assessment in people receiving long-term metformin, particularly when anemia or peripheral neuropathy is present. For older adults who have taken metformin for more than four years, the ADA guidance recommends annual B12 monitoring.
A practical question for the next appointment is: “I have been taking metformin for several years. When was my vitamin B12 last checked?”
Do not automatically start high-dose supplements because you use metformin. Discuss testing and treatment with your doctor.
Kidney Function Matters Too
Metformin leaves the body largely through the kidneys. Kidney function therefore affects how safely the medicine can be used.
The number patients should learn to recognize on their laboratory report is eGFR, or estimated glomerular filtration rate.
The U.S. Food and Drug Administration recommends obtaining an eGFR before starting metformin and at least annually while taking it. Kidney function may need more frequent monitoring in older people and others at greater risk of renal impairment.
An eGFR below 30 mL/min/1.73 m² is an important threshold. Metformin is contraindicated below that level. If the eGFR falls below 45 while a person is already taking metformin, the FDA advises clinicians to reassess the benefits and risks of continuing treatment.
Patients do not need to calculate any of this themselves. Ask: “What is my eGFR, and is my present metformin dose appropriate for my kidney function?”
When Metformin Upsets the Stomach
Metformin has another familiar problem. The gut sometimes objects.
Diarrhoea, abdominal discomfort and reduced appetite can occur. For some people these effects become troublesome enough to interfere with daily life.
I experienced bowel problems myself after changes in treatment. My physician eventually moved me to a sustained-release formulation.
The 2026 ADA Standards note that extended-release metformin can be used as an alternative for older adults experiencing gastrointestinal problems with treatment. But persistent diarrhoea should not simply be labelled “the metformin problem” forever.
Tell your doctor when the symptoms started. Explain whether they followed a dose increase and whether they improved after switching formulations. The timing gives the doctor useful information.
Illness Changes the Equation
A tablet that is appropriate on an ordinary Tuesday may require a different plan when you are vomiting, unable to drink or losing substantial fluid through diarrhoea. Dehydration can affect kidney function.
The 2026 ADA Standards say clinicians should consider temporarily holding metformin and SGLT2 inhibitors when a person cannot maintain oral intake or when there is concern about acute kidney injury.
The sensible approach is to ask your doctor for a sick-day plan before you become sick. Ask exactly what to do if you develop persistent vomiting or significant diarrhoea. Ask what happens if you cannot eat or drink normally. Write the instructions down.
If You Also Take Empagliflozin, Check the Instructions
Empagliflozin belongs to a group of medicines called SGLT2 inhibitors. These medicines are now used for more than glucose control. Depending on the patient’s condition, empagliflozin can provide cardiovascular, heart-failure and kidney benefits.
Current FDA prescribing information for Jardiance, the reference brand of empagliflozin, gives 10 mg once daily in the morning as the recommended starting dose. For additional glucose control, it can be increased to 25 mg once daily in appropriate patients.
If you think you have been told to take empagliflozin 10 mg twice daily, do not simply change the dose after reading an article online. Take the medicine box and prescription to your doctor or pharmacist and ask them to confirm exactly what was intended.
Five Tests Worth Discussing
A long-term metformin user does not necessarily need every possible blood test at every visit. A few measurements, however, deserve a conversation.
- HbA1c to assess longer-term glucose control.
- Serum creatinine and eGFR to assess kidney function.
- Vitamin B12, particularly after several years of metformin treatment.
- Complete blood count (CBC), which can help identify anemia and other abnormalities.
- Urine albumin-to-creatinine ratio (UACR), an important test for detecting kidney damage associated with diabetes.
Your doctor may order additional investigations depending on your health, medicines and previous results. The point is not to arrive at the clinic demanding five tests. The point is to ask whether they are due.
Take Your Medication History With You
Patients often tell doctors, “I take one sugar tablet in the morning and another at night.” That is not enough information.
Before your appointment, photograph the front and back of every medicine box. Better still, take the medicines with you. Write down the exact dose and when you take each tablet.
“I have been taking metformin-containing treatment for several years. My dose and formulation have changed because I developed bowel problems. Could we review whether my current dose remains appropriate, check my kidney function and B12 status, and give me instructions for what to do with my diabetes medicines if I develop vomiting, diarrhoea or dehydration?”
That short history tells the doctor much more than “metformin doesn’t suit me.”
Do Not Stop a Useful Medicine Because of an Internet Article
Metformin has been used for decades and remains an important treatment for type 2 diabetes. Long-term use does not automatically mean that something has gone wrong.
Monitoring is the point.
A person who has taken metformin for years should know whether kidney function remains adequate. B12 deserves attention after prolonged treatment. Persistent bowel symptoms deserve a proper discussion rather than silent endurance.
I reached this subject by looking at my own medication history. The exercise reminded me how easily years of treatment disappear behind the latest prescription.
Take the boxes to the doctor. Take your laboratory reports too. Then ask the questions that years of treatment sometimes teach us to forget.
Sources
- American Diabetes Association: Older Adults, Standards of Care in Diabetes 2026
- American Diabetes Association: Glycemic Goals, Hypoglycemia and Hyperglycemic Crises, 2026
- U.S. FDA: Metformin and kidney function safety recommendations
- U.S. FDA: Jardiance (empagliflozin) prescribing information
Medical note: This article provides general educational information and does not replace individual medical advice. Do not stop, start or change the dose of metformin, empagliflozin or another prescribed medicine without discussing it with your treating physician.
