Metformin Side Effect That Needs to Stay on Your Radar

Metformin is a common medication used to treat type 2 diabetes. It’s well-known for its ability to lower blood sugar levels effectively. However, many people who take metformin long-term may not realize it can lead to a deficiency in vitamin B12. Moreover, a recent case report uncovered by the DrugCard platform highlights the real-world consequences of undiagnosed B12 deficiency in a long-term metformin user. This article explores how metformin affects vitamin B12 levels, the symptoms of deficiency, and regulatory updates.

Why Long-Term Metformin Use Can Cause Vitamin B12 Deficiency

Metformin improves insulin sensitivity and reduces glucose production in the liver. However, long-term use of metformin has been linked to vitamin B12 deficiency. The drug can interfere with the absorption of B12 in the small intestine, leading to a gradual depletion of this vital nutrient.

What Is Vitamin B12, and Why Is It Important?

Vitamin B12 is essential for nerve function, the production of red blood cells, and DNA synthesis. When levels are low, it can result in several health problems, including:

Neuropathy: Tingling or numbness in the hands and feet.

Fatigue: Low red blood cell production causes weakness and tiredness.

Cognitive Issues: Memory problems and confusion, particularly in older adults.

Anemia: Insufficient B12 can lead to a lack of red blood cells.

A Real-World Case: When a Fall Uncovered a Hidden Deficiency

A recent case report in the medical literature identified by the DrugCard platform highlights the serious consequences of undiagnosed metformin-induced vitamin B12 deficiency.

A 68-year-old man with diabetes had been taking metformin for 14 years. His diabetes was well-controlled, but over the past six months, he had frequent falls and increasing unsteadiness.

One day, he fell onto a stone surface and suffered a severe thigh injury. He had no recent chest pain, palpitations, or loss of consciousness, but his family had noticed mild forgetfulness in recent months.

A CT scan showed a Morel-Lavallée lesion – a serious internal bruising injury caused by trauma. These injuries typically occur due to high-impact trauma, such as sports accidents or motor vehicle crashes. However, in this case, a relatively minor fall led to a severe injury, emphasizing the profound effects of B12 deficiency on balance, proprioception, blood vessel integrity, and wound healing.

Regulatory Update on Metformin and Vitamin B12 Deficiency

In June 2022, the MHRA (UK) issued new guidance on vitamin B12 deficiency linked to long-term metformin use, highlighting the need for increased awareness and monitoring. Similar regulatory actions have been taken in France, Sweden, and Switzerland.

Previously classified as a very rare side effect, reduced B12 absorption due to metformin was reassessed across Europe after new research suggested it is more common than previously thought. Based on this evidence, the MHRA concluded that B12 deficiency should now be listed as a common adverse drug reaction, affecting up to 1 in 10 metformin users.

Studies show that 4.3% to 30% of metformin users develop B12 deficiency, with the risk increasing with higher doses, longer treatment duration, and pre-existing risk factors.

Managing and Preventing Vitamin B12 Deficiency in Metformin Users

Monitoring your vitamin B12 levels is essential if you’re using metformin long-term. Here are some strategies to manage and prevent deficiency:

Regular Testing: Periodic blood tests for vitamin B12 levels should be part of routine care for long-term metformin patients.

Vitamin B12 Supplements: Vitamin B12 can help restore normal levels if a deficiency is found. Oral supplements are commonly prescribed, but in severe cases, injections may be needed.

Dietary Adjustments: While supplements are key, incorporating foods rich in vitamin B12, like meat, dairy, and fortified cereals, can also help.

Conclusion: Stay Informed About Metformin and Vitamin B12 Deficiency

Metformin is essential for managing type 2 diabetes, but its long-term use can lead to vitamin B12 deficiency. Healthcare providers must be aware of the risks and monitor patients regularly. With recent regulatory updates, it’s clear that vigilance is key in managing this hidden side effect. By staying informed and testing B12 levels regularly, the risks associated with metformin use can be effectively minimized.