Can I take Metformin and Mirtazapine together?

Why this happens

Mirtazapine can sometimes cause metabolic changes, such as increased appetite or changes in how the body responds to insulin. This can work against the blood-sugar-lowering effects of metformin.

What you should do

You can usually take metformin and mirtazapine together, but you should monitor your blood sugar levels more closely when you first start mirtazapine or if your dose changes.

If you notice your blood sugar readings are consistently higher than usual, or if you feel unusually thirsty or tired, speak to your GP. They may need to adjust your metformin dose or give you advice on managing your weight.

Important precautions

Depression and mental health disorders

Mirtazapine can increase thoughts of self-harm or suicide, particularly when you first start taking it or when your dose is changed. You must tell someone you trust that you are taking this medicine and seek medical help immediately if your mood worsens or you have distressing thoughts.

Lactic acidosis

Metformin can cause a rare but serious build-up of acid in the blood. Seek urgent medical help if you experience extreme tiredness, muscle pain, or difficulty breathing. This risk is higher if you have severe kidney problems or drink excessive alcohol.

Severe dehydration or infection

If you develop severe vomiting, diarrhoea, or a high fever, you must temporarily stop taking metformin and contact your doctor to prevent kidney strain.

Medical scans using iodine contrast dye

If you are having an X-ray or scan involving an injection of iodine contrast dye, you must stop taking metformin before or at the time of the test to prevent sudden kidney failure.

Serotonin Syndrome

Taking mirtazapine alongside other serotonergic substances (such as serotonin supplements) significantly increases the risk of serotonin syndrome, a potentially life-threatening condition. Symptoms include agitation, hallucinations, rapid heartbeat, and muscle stiffness.

Low white blood cell count (Agranulocytosis)

Mirtazapine can rarely cause a serious drop in white blood cells. You must contact a doctor immediately if you develop signs of infection, such as a high fever, severe sore throat, or mouth ulcers.

Food and drink warnings

Alcohol

It is best to avoid or strictly limit alcohol while taking metformin. Drinking alcohol with this medicine increases the risk of a rare but serious condition called lactic acidosis (a build-up of lactic acid in the blood). It also increases the risk of low blood sugar (hypoglycaemia).

It is best to avoid or strictly limit alcohol while taking mirtazapine. Both alcohol and mirtazapine cause drowsiness and can affect your coordination; combining them significantly increases these effects, making you feel very sleepy and increasing the risk of accidents.

Vitamin B12 absorption

Long-term use of metformin can prevent your body from absorbing enough vitamin B12 from your food. You may need to have your B12 levels checked by your doctor or take a supplement if you develop symptoms like extreme tiredness or a sore tongue.

General Food Advice

Metformin should be taken with or just after a meal or snack. This helps to reduce the risk of common side effects such as stomach upset, indigestion, or nausea.

Using other medicines

Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.

Disclaimer

This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.