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Which Drugs Cause Weight Gain?

Medically reviewed on Nov 29, 2017 by L. Anderson, PharmD.

Losing weight, or maintaining a healthy weight, can be a battle for many patients. The US Centers for Disease Control and Prevention (CDC) notes that overall, 36.5% percent of U.S. adults (or 78.6 million) are obese and about 17% of children and adolescents (or 12.7 million) are obese.

Body mass index (BMI) is a tool used to screen for obesity or overweight. For adults, if your BMI is 30 or higher, it falls within the obese range, and if it's 25.0 to <30, it's in the overweight range. For children, obesity is defined as a BMI at or above the 95th percentile for children and teens of the same age and sex, and overweight is defined as a BMI at or above the 85th percentile and below the 95th percentile. 

Aging, lack of exercise, and food choices are all culprits in the battle to keep weight down. However, some very common medications can also lead to weight gain. For example, prescription drugs found in these various classes can all add on unwanted pounds:

Some medications are more common than others to boost weight, and not all patients will gain weight from every drug that has weight gain listed as a side effect. However, it is important to understand your risk.

Learn More: Do My Medications Cause Weight Gain?

How Do Prescription Drugs Cause Weight Gain?

For many drugs, it is not known exactly what causes the weight gain. Some medications can increase appetite, cause fluid retention, or slowly lead to weight gain over a period of time due to fatigue and lower activity. Drugs that trigger increases in appetite may work in the brain and affect the satiety (fullness) center. 

It is often difficult to distinguish between weight gain from a drug and weight gain from other reasons, like diet or lack of exercise, because it can be a slow process. Some conditions, like depression, can lead to weight loss or, more rarely, weight gain, depending upon the person. Weight gain may increase the chance for high cholesterol, hypertension (high blood pressure), and type 2 diabetes. If a rapid weight gain occurs in a short period of time, a physician should be contacted for evaluation, especially if you are at risk for heart disease or high blood pressure.

Don't stop taking any medication without talking to your doctor first. If you have a concern about weight gain with medicine, talk to your doctor. In many cases, you may be able to switch to a different medication or use a lower dose of the drug. Together you can make sure the benefits of the medicine outweigh the risks from any weight gain. You may need to have a multi-faceted approach too: an increase in exercise, attention to diet, and limiting salt intake may also be recommended.

Patients should ask their healthcare provider about the potential for weight gain before a new medication is prescribed. And remember, medications may affect patients differently, and not every patient will gain weight. Worries about weight gain or loss should not be the main deciding factor for needed medical treatment.

What Drugs Can Lead to Weight Gain?


  • Usually, a physician can choose among many alternatives in the antidepressant class if weight gain is an issue. Some antidepressants may lead to weight gain by interfering with the neurotransmitter serotonin that may control appetite.
  • Older antidepressants, known as tricyclic antidepressants (TCAs) are notorious for increasing appetite and for causing weight gain. Examples of TCAs include amitriptyline (Elavil) and nortriptyline (Aventyl, Pamelor). TCAs affect neurotransmitters in the brain and exhibit antihistamine activity, which can boost appetite and lead to weight gain. TCAs are also be used to treat migraine headaches.
  • Another class of antidepressants, called selective serotonin reuptake inhibitor (SSRI), are not always linked with weight gain, but some frequently prescribed SSRIs, like paroxetine (Paxil), can cause weight gain. Fluvoxamine (Luvox) has also been tied to weight gain. Some SSRIs are more weight neutral, such as fluoxetine (Prozac), citalopram (Celexa), escitalopram (Lexapro), or sertraline (Zoloft).
  • Mirtazapine (Remeron) is an antidepressant that boosts serotonin, like SSRIs, but also has an antihistamine effect that may lead to weight gain.
  • Bupropion (Wellbutrin) is antidepressant that is actually associated with weight loss, and it's also an antidepressant linked with less sexual side effects. Venlafaxine (Effexor) and duloxetine (Cymbalta) also have more neutral effects on weight gain.


  • Antihistamines, such as cetirizine (Zyrtec) and fexofenadine (Allegra), selectively antagonize histamine H1 receptors. These drugs, which are available without a prescription, have been associated with weight gain. Antihistaminic activity can boost appetite, as noted with several other drugs that cause weight gain.
  • A study compared the use of antihistamines and the risk of obesity. Users of cetirizine (Zyrtec) and fexofenadine (Allegra) had significantly greater weight, BMI, waist circumference, and insulin levels.

Antipsychotics/Mood Disorder:

  • Antipsychotics are frequently linked with weight gain. Examples in this drug class include the atypical antipsychotics olanzapine (Zyprexa) and risperidone (Risperdal). Clozapine (Clozaril), an older, atypical antipsychotic has also been linked with significant weight gain. Patients may gain from 7% to 10% of their body weight. These drugs may have antihistamine activity and also block serotonin, which may contribute to the weight gain effect. Older "typical" antipsychotics by the name of haloperiodol (Haldol), chlorpromazine (Thorazine), and thioridazine (Mellaril) can also cause weight gain, but these drugs are used less frequently due to movement disorder side effects.
  • Research by Huang and colleagues has shown an enzyme called AMP-kinase is elevated in the brain of patients who use antipsychotics. AMP-kinase can block the brain histamine-1 receptor, which will boost appetite and may lead to weight gain.
  • Many of the antipsychotics may impair glucose (sugar) control and lead to insulin resistance, impaired glucose tolerance and type 2 diabetes. However, these drugs may be necessary for treatment of bipolar disorder, severe depression, or schizophrenia and patients or caregivers must speak with the physician before stopping treatment. For many mental health disorders, drug treatment may be absolutely necessary and the risk of stopping the drug may be greater than the risk associated with weight gain.
  • Ziprasidone (Geodon) and aripiprazole (Abilify) are more weight neutral antipsychotics, but still may alter blood glucose.

Antihypertensives - Beta Blocker (Blood Pressure):

  • The class of high blood pressure (hypertension) drugs known as beta blockers has been associated with weight gain. Common examples of this class are metoprolol (Lopressor) and atenolol (Tenormin).
  • Many of the older beta blocker drugs can lead to fatigue, which may be responsible for some of the weight gain. Patients may be tired, have lack of energy, and in general slow down, which may affect the number of calories burned each day.
  • Other blood pressure medications like the calcium channel blockers and ACE inhibitors are less likely to cause weight gain.

Birth Control:

  • In general, the birth control pill is not usually associated with weight gain, especially the newer pills with lower doses of estrogen and progestin.
  • One form of birth control, the birth control shot known as medroxyprogesterone (Depo-Provera) that is given every 3 months, can cause significant weight gain in some women.


  • Oral corticosteroids (glucocorticoids) may carry a risk of weight gain with high dose and long-term use and higher doses. Oral corticosteroids are used for severe asthma, or painful inflammatory conditions such as rheumatoid arthritis or inflammatory bowel disease.
  • Local injectable corticosteroids, such as might be done in the knee joint or spinal column for inflammation, and inhaled corticosteroids used for asthma are not linked with weight gain.
  • Steroids can affect the metabolic rate, and lead to increased appetite and overeating. Examples of corticosteroids include prednisone (Sterapred), methylprednisolone (Medrol Dosepak) and triamcinolone (Kenalog).

Diabetes Medications:

  • Certain oral medications for type 2 diabetes, such as glyburide (DiaBeta) and glipizide (Glucotrol), members of the sulfonylurea class, can lead to weight gain. These agents may increase insulin production, which can lower blood sugar levels and result in an elevated appetite.
  • Injectable insulin itself can also lead to weight gain, as insulin use allows glucose to enter your cells instead of staying in your blood. But too many calories in the form of glucose will lead to weight gain. Excess glucose ends up as fat if it's not burned off with exercise.
  • Other drugs used in the treatment of type 2 diabetes can lead to weight gain and fluid retention. Examples include pioglitazone (Actos) and rosiglitazone (Avandia) which are in the class thiazolidinediones.
  • Metformin (Glucophage), exenatide (Byetta), and sitagliptin (Januvia) are more likely to be weight neutral or associated with weight loss. 

Seizures/Mood Stabilizers:

  • Valproic acid (Depakote, Depakene) is used to treat epilepsy (seizures), bipolar disorder and for migraine prevention. Valproic acid appears to boost appetite and may result in a 10 pound or more weight gain. Topiramate (Qudexy XR Sprinkle, Topamax), used for seizures and migraine headaches, might actually cause weight loss in some people.
  • Lithium (Lithobid) is also commonly used for mood disorders and is associated with weight gain.

Common Drugs That May Lead to Weight Gain

Medication Generic Name Drug Class or Use
Paxil paroxetine SSRI Antidepressant
Zoloft sertraline SSRI Antidepressant
Elavil amitriptyline Tricyclic Antidepressant
Remeron mirtazapine Antidepressant
Clozaril clozapine Antipsychotic/Mood Stabilizer
Zyprexa olanzapine Antipsychotic/Mood Stabilizer
Risperdal risperidone Antipsychotic/Mood Stabilizer
Seroquel quetiapine Antipsychotic/Mood Stabilizer
Lithobid lithium Mood Stabilizer
Depakene, Depakote valproic acid, divalproex Seizure Disorder/Migraines/Mood Stabilizer
Neurontin gabapentin Seizure Disorder
Tegretol carbamazepine Seizure Disorder/Mood Disorder
Lopressor metoprolol Antihypertensive-Beta Blocker (blood pressure)
Tenormin atenolol Antihypertensive-Beta Blocker (blood pressure)
Inderal propranolol Antihypertensive-Beta Blocker (blood pressure)
Norvasc amlodipine Antihypertensive-Beta Blocker (blood pressure)
Catapres clonidine Alpha-2 Adrenergic Agonist (blood pressure,
Actos pioglitazone Thiazolidinediones (diabetes)
Avandia rosiglitazone Thiazolidinediones (diabetes)
Amaryl glimepiride Sulfonylureas (diabetes)
Novolog, Lantus, Humalog (various brands) insulin Diabetes
Diabeta glyburide Sulfonylureas (diabetes)
Glucotrol glipizide Sulfonylureas (diabetes)
Deltasone, Medrol, Solu-Cortef prednisone, methylprednisolone, hydrocortisone Corticosteroid
Allegra fexofenadine Antihistamines
Zyrtec cetirizine Antihistamines
Depo-Provera Contraceptive medroxyprogesterone Contraceptives

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