Yes. Some medicines can contribute to weight gain, although the effect depends on the specific medicine, the dose, how long it is used, and the individual taking it. Weight gain may happen because a medicine increases appetite, causes the body to retain fluid, or affects metabolism and energy use. In other cases, the timing may be coincidental and another health or lifestyle factor may be responsible.
If you are concerned about tablets causing weight gain, do not stop a prescription medicine on your own. Instead, note when the weight change began, check the medicine’s patient information leaflet, and discuss the change with your doctor or pharmacist.
You can also use the Symptom-Led Side Effects hub to explore other symptoms or read the more detailed medicine causing weight gain guide.
How tablets Causing Weight Gain can be linked to medicines or supplements
A change on the scale after starting a medicine does not automatically prove that the medicine caused it. However, the timing and pattern can provide useful clues.
Medicines can affect weight in different ways. For example, mirtazapine can increase appetite, while corticosteroids such as prednisolone can increase appetite as well as cause water retention. Some antipsychotic medicines are also associated with weight and metabolic changes.
Possible medicine categories
Categories in which weight gain may occur with some medicines include:
- Antidepressants. Weight gain is listed among the possible side effects of antidepressants, although individual medicines differ considerably. Mirtazapine, for example, may increase hunger and contribute to weight gain.
- Antipsychotic medicines. Some antipsychotics can cause increased appetite, weight gain or broader metabolic effects. Olanzapine, for example, can increase hunger and lead to weight gain.
- Corticosteroids. Medicines such as prednisolone may increase appetite and cause the body to retain more water, particularly when used for longer periods.
- Certain diabetes medicines. Weight effects vary greatly between diabetes treatments. Some people gain weight while taking medicines such as gliclazide, whereas metformin generally does not cause weight gain.
- Some medicines used for nerve pain, epilepsy or anxiety. Pregabalin can increase appetite and is associated with weight gain in some people.
This is not a complete list. The safest way to assess a specific product is to check its approved patient leaflet and ask a pharmacist or doctor whether weight gain is a recognised effect.
Herbal, complementary and other supplements should also be included when you discuss your medicines with a healthcare professional. Information about the effects and interactions of some complementary products may be limited, so “natural” should not automatically be interpreted as risk-free.
Timing clues
Consider what happened around the time the weight change began.
Useful questions include:
- Did the change begin after starting a new medicine?
- Was the dose recently increased or changed?
- Has your appetite changed noticeably?
- Have you become sleepier or less active since starting treatment?
- Is the weight increasing gradually over weeks or months?
- Did the increase happen rapidly over only a few days?
- Are your ankles, feet, hands, face or abdomen also swollen?
- Are you taking more than one medicine or supplement?
A timeline does not establish the cause, but it can give your doctor or pharmacist useful information when deciding what should be investigated.
Medicines and product categories that may be associated with this symptom
The phrase “tablets causing weight gain” covers many different situations. Finding the correct medicine category is more useful than assuming that all tablets have the same effect.
Mental health medicines
Antidepressants and antipsychotics differ substantially in their effects on appetite and weight. Even medicines used for similar conditions can have different side-effect profiles. For example, mirtazapine and olanzapine are both associated with increased appetite and weight gain, while the effect of another medicine may be different.
If the medicine is being used for depression, bipolar disorder, schizophrenia, anxiety or another mental health condition, changes should be discussed with the prescribing clinician rather than made independently.
Corticosteroids
Steroid tablets such as prednisolone can contribute to weight gain through increased appetite and water retention. The chance of steroid-related side effects generally becomes more important with higher doses or longer treatment periods.
Because corticosteroids may require careful dose reduction in some circumstances, they should not be stopped suddenly without appropriate medical advice.
Diabetes medicines
Diabetes treatments should not be treated as one group when considering weight. Some treatments may be associated with weight gain, while others are relatively weight-neutral or can be associated with weight loss.
For example, some people taking gliclazide gain weight, while NHS guidance states that metformin does not cause weight gain.
If you have diabetes, do not change treatment simply because your weight changes. Altering diabetes medication without professional advice can affect blood-glucose control.
Nerve-pain and related medicines
Pregabalin, which may be used for conditions including nerve pain and epilepsy, can increase hunger and contribute to weight gain in some people. Swelling of the arms or legs can also occur.
If both swelling and weight gain develop, tell your doctor or pharmacist rather than assuming the change is only body fat.
How to choose the right next guide
Start with the name of the medicine or active ingredient on the box, label or prescription. Then check whether the medicine has its own side-effect information.
If you are not sure which medicine may be involved, the broader medicine causing weight gain guide can help you understand the issue before you speak to a healthcare professional.
Red flags: when this symptom may need urgent medical attention
Gradual weight gain without other symptoms is usually different from rapid weight gain accompanied by swelling, breathing problems or a severe medicine reaction.
Rapid weight gain can sometimes reflect fluid accumulation rather than an increase in body fat. Unexplained weight gain together with swollen feet and shortness of breath should be medically assessed.
Weight gain with swelling or breathing problems
Seek prompt medical attention if a rapid increase in weight is accompanied by:
- new or worsening shortness of breath;
- significant swelling of the feet, ankles, legs or abdomen;
- difficulty breathing when lying down;
- sudden worsening of breathing symptoms; or
- severe weakness, dizziness or fainting.
Fluid accumulation can occur in serious medical conditions, including problems affecting the heart or lungs, and should not simply be attributed to a tablet without assessment.
Emergency medicine-reaction symptoms
Regardless of whether weight gain is also present, get immediate medical help for symptoms such as:
- trouble breathing;
- swelling of the face, lips, tongue or throat;
- severe chest pain;
- fainting or loss of consciousness;
- seizures;
- a severe or rapidly spreading rash;
- severe bleeding;
- suicidal thoughts or an immediate risk of self-harm;
- suspected overdose; or
- symptoms that are rapidly becoming severe.
These symptoms should not be managed by waiting for an online explanation.
What to track before speaking to a doctor or pharmacist
Good records can make it easier for a healthcare professional to assess whether a medicine might be contributing to the change.
What information to record
Write down:
- the name and strength of every prescription medicine you use;
- over-the-counter medicines;
- vitamins, herbal remedies and supplements;
- when each product was started;
- any recent dose changes;
- your approximate weight before the change began;
- dates and weight measurements if you have them;
- whether your appetite has increased;
- any swelling of your feet, ankles, hands, face or abdomen;
- changes in thirst or urination;
- changes in sleep or activity;
- other new symptoms; and
- any other major changes that happened at about the same time.
Try to measure weight under reasonably similar conditions rather than repeatedly checking throughout the day. The purpose is to identify a trend that you can discuss with a healthcare professional, not to diagnose the cause yourself.
When to contact a doctor or pharmacist
Speak to a pharmacist or doctor if the weight gain is persistent, significant for you, unexplained, or began after starting or changing a medicine.
A pharmacist can help check whether weight gain is listed for your medicine, identify possible medicine interactions and explain the patient information leaflet. A doctor may also need to consider whether another health condition could explain the change.
MedlinePlus advises contacting a healthcare professional about excessive unexplained weight gain and about weight gain accompanied by symptoms such as swollen feet and shortness of breath.
What not to do without medical advice
Concern about weight gain can make it tempting to stop treatment immediately. That is not always safe.
Do not stop a prescription medicine suddenly
Stopping certain medicines abruptly can cause withdrawal symptoms, allow the condition being treated to worsen, or create other health risks. For example, NHS guidance notes that antidepressants such as mirtazapine are normally reduced gradually when treatment is being stopped.
Do not skip doses, reduce the dose, double doses, or change the schedule simply to see whether your weight changes unless a healthcare professional has advised you to do so.
Do not assume the medicine is definitely responsible
Weight can change for many reasons. Medicines are only one possible contributor.
A pattern that begins after treatment starts may make a medicine-related effect worth investigating, but it does not prove cause and effect. Your doctor may need to consider other symptoms, health conditions, lifestyle factors and medicines before reaching a conclusion.
Do not replace prescribed treatment with supplements
Avoid replacing a prescribed medicine with a herbal or complementary product without professional advice. Some supplements can interact with medicines, and safety information for complementary remedies may be less complete than for authorised medicines.
If you are using a supplement when unexplained weight changes occur, tell your pharmacist or doctor exactly what product you use.
Related side-effect guides and reporting options in South Africa
If you suspect that a medicine has contributed to weight gain, the next step is usually to identify the product, record the timing and accompanying symptoms, and discuss your concern with a healthcare professional.
For broader medicine-safety information, visit the medication side effects guide.
If you believe you may have experienced an adverse reaction, you can also read how to report side effects in South Africa.
What information to record
SAHPRA encourages patients and healthcare professionals to report suspected medicine side effects. You do not have to prove that the medicine caused the reaction before it can be reported. Useful information includes details of the suspected medicine or health product, what happened and information that allows the report to be followed up.
Keep the medicine packaging if possible, because the exact product name, strength and other details can be useful.
Where reporting fits into medicine safety
Reporting a suspected reaction is different from receiving medical treatment. If you are unwell, speak to a doctor or pharmacist first, or seek emergency care when symptoms are severe.
SAHPRA states that patients and consumers can report adverse events directly to the Authority. Its Med Safety App is designed to allow members of the public as well as healthcare professionals to submit suspected adverse drug reactions.
Reports help regulators monitor medicine safety, but submitting a report does not prove that a particular product caused the weight gain or other symptom.
Frequently asked questions
Is weight gain a common medicine side effect?
It depends entirely on the medicine. Weight gain is recognised with some medicines, including particular antidepressants, antipsychotics, corticosteroids, diabetes medicines and medicines such as pregabalin. Other medicines in the same broad treatment areas may have little or no tendency to increase weight.
Check the information for the exact medicine rather than assuming the effect applies to an entire category.
How long can medicine-related weight gain last?
There is no single timeframe. It depends on the medicine, why the weight is changing, how long treatment continues and individual factors.
For example, corticosteroid-associated weight gain may involve both increased appetite and fluid retention, while another medicine may influence appetite differently.
If your weight continues to increase or the change is concerning, discuss it with your doctor or pharmacist.
Should I stop the medicine if I am gaining weight?
Not without medical advice. The risks of abruptly stopping treatment may be more serious than the weight change itself.
Speak to your doctor or pharmacist. Depending on the medicine and your circumstances, they can assess the likely cause and discuss appropriate options without compromising treatment safety.
When should I seek help?
Arrange medical advice for unexplained or persistent weight gain, particularly if it started after a medicine change.
Seek more urgent medical care if weight rises rapidly and you also develop significant swelling or shortness of breath. Get emergency help for trouble breathing, severe chest pain, swelling of the face or throat, fainting, seizures, severe rash, severe bleeding, suicidal thoughts or suspected overdose.
What are the most important things to know about tablets causing weight gain?
Some tablets can contribute to weight gain, but the effect varies by medicine and person. Look at the timing, appetite changes, swelling and other symptoms; record all medicines and supplements you use; and discuss persistent or concerning changes with a pharmacist or doctor.
Do not stop prescribed treatment or adjust the dose on your own. Rapid weight gain with swelling or breathlessness needs medical attention rather than being assumed to be an ordinary medicine side effect.
A practical next step
If you think a tablet may be affecting your weight, write down the medicine name, when you started it, any dose changes, your weight trend and any other symptoms. Check the patient information leaflet and take that information to your pharmacist or doctor.
For serious or rapidly worsening symptoms, seek urgent medical help. For suspected medicine reactions in South Africa, SAHPRA also provides routes for patients and healthcare professionals to report adverse events.
Medical information notice: This page provides general educational information about possible medicine side effects. It cannot determine whether a particular medicine is causing your weight gain and does not replace advice from a doctor or pharmacist. Do not start, stop or change the dose of a prescribed medicine based on this information alone.