The NHS has issued an urgent warning for individuals taking metformin, a widely prescribed medication for type 2 diabetes and gestational diabetes, to seek immediate medical advice if they observe a specific skin symptom.
Metformin, used by approximately 200 million people globally, can cause a rare but serious side effect: jaundice. This condition, characterized by yellowing of the skin or the whites of the eyes, may signal liver complications. The NHS advises patients to call their doctor or dial 111 straight away if they notice such symptoms.
Jaundice may be less obvious on brown or black skin, so individuals with darker skin tones should be particularly vigilant. Other serious symptoms requiring urgent attention include a general feeling of being unwell, severe tiredness, fast or shallow breathing, feeling cold, and a slow heartbeat.
Common side effects of metformin are generally mild and manageable, including nausea, vomiting, diarrhoea, stomach ache, loss of appetite, and a metallic taste in the mouth. However, if these persist or cause concern, patients should consult a healthcare professional.
In extremely rare cases, metformin can cause a serious allergic reaction (anaphylaxis). Signs include sudden swelling of the lips, mouth, throat, or tongue; difficulty breathing; a tight throat; blue or pale skin; confusion; drowsiness; or fainting. In such events, the NHS advises calling 999 immediately.
Patients should also be aware of potential vitamin B12 deficiency and low blood sugar, which may require medical consultation.
