Medicines That Can Change Weight

Overview

Weight changes can be a side effect of a medicine. This page lists medicine groups that major health sources link to weight changes, so you can raise the question with your prescriber. It is not a reason to stop anything. Never stop or change a prescribed medicine on your own because of weight. Ask the prescriber or pharmacist first. For example, NHS advises talking to a doctor before stopping semaglutide, not stopping suddenly, and says that for people with type 2 diabetes, stopping could affect blood sugar. [1]

Medicines that may contribute to weight gain

NIDDK says some medicines can affect energy balance by making you hungry or making your body burn fewer calories. [2]

Not everyone who takes these medicines gains weight, and the sources do not give how often it happens for each one.

Medicines linked to weight loss or reduced appetite

• Levothyroxine, often used for an underactive thyroid, is listed by NHS among medicines whose side effects can cause unintentional weight loss. [5]
• MedlinePlus lists medicines including chemotherapy medicines and thyroid medicines among causes of appetite loss. [6]
• Some prescription weight-management medicines are intended to reduce appetite; see Weight-loss medications and medical care. NHS lists common side effects of semaglutide as nausea, vomiting, constipation, diarrhea, tiredness and hair loss. [1]

If weight loss is not intended, see Unintentional weight loss.

What to do if you think a medicine is affecting your weight

1. Keep taking it as prescribed until you have spoken to the prescriber. [1] (This is NHS advice for semaglutide; the principle applies broadly: ask first.)
2. Write down what changed, when it started and what else changed (sleep, activity, stress).
3. Ask whether a different medicine, a different dose, or extra support (such as a dietitian or a weight management program) is an option. NIDDK says a health care professional may review the medicines and supplements you take to see whether they affect your weight. [7]
4. Tell your clinician about supplements and herbs. See How interactions work and Talking with a health professional.

Medicines, health conditions and weight often travel together

Health problems such as polycystic ovary syndrome, Cushing's syndrome, hypothyroidism and depression can also lead to weight gain, so a change in weight after starting a medicine may not be due to the medicine alone. [2]

Evidence note

Insufficient evidence in the sources I read to rank medicines within each group by how much weight change they cause, or to say which alternatives are best. That is a question for your prescriber, who can weigh benefits and side effects.

When to get help

Contact your prescriber if weight or appetite changes are fast, large or distressing, or if new symptoms appear after starting a medicine. NHS advises a GP visit for weight loss without trying. [5] Report side effects using the route your health system provides; for US dietary supplements and products, see Side effects, allergic reactions and reporting.