10 Medications That May Cause Weight Gain

These days, there’s a pill for everything. Some of the most popular are pills to lose weight — although you’ll want to be careful. A good number of them amount to snake oil. But some are actually effective when used correctly. Unfortunately, there are also popular medications that can cause you to gain weight. Unintentionally, that is.

Here are 10 popular medications and drugs, both prescription and over the counter, that are associated with weight gain.

1. Prozac

Two bottles of Prozac are seen on a pharmacy shelf

Prozac can affect your waistline. | Stephen Chernin/Getty Images

One of the most well-known drugs tied to weight gain is Prozac. Prozac is a commonly used and prescribed antidepressant. It’s not the only antidepressant that’s been associated with weight gain (as you’ll see), but on a brand-name level, it may be the most popular. According to WebMD, approximately 25% of antidepressant users will gain weight — often up to 10 pounds or more.

2. Allegra

Pile of prescription pills spilling from open pill bottle.

Allegra can affect your weight. | iStock.com/ANDROMACHI

Millions of people suffer from seasonal or chronic allergies. One of the more popular and common treatments is a drug called Allegra, which is available pretty much anywhere. Unfortunately for allergy sufferers, Allegra can also cause you to gain weight. One study showed that people who take antihistamines regularly weigh between 4.4 and 9.5 pounds more than those who don’t.

3. Zyrtec

Medicine Pill removed from blister

Zyrtec may also cause issues. | iStock.com/Thanmano

Along with Allegra, Zyrtec is another antihistamine that is associated with weight gain. There are other side-effects that antihistamines like Zyrtec will cause as well, but gaining weight is typically one people don’t expect. The easiest explanation as to why, is that these types of drugs target certain receptors that not only deal with histamine, but are also hardwired into the workings of our appetites.

4. Paxil

Drugs spread out on a table

Expect to gain weight on Paxil. | iStock.com/loooby

Away from antihistamines and back to antidepressants. Paxil, an SSRI antidepressant similar to Prozac, can also cause some users to pack on the pounds. Some people who have used Paxil regularly have reported very serious and significant weight gain. It’s not all directly caused by the drug, but these types of medications can be an underlying factor.

5. Birth control

three types of birth control

Birth control is well-known for this side effect. | iStock.com

A staple for millions, birth control is often blamed for weight gain. There’s good news, though. While birth control can cause you to pack on a few pounds in some cases, it’s usually a passing phase. The extra pounds can often be traced to extra fluid retention. It’s water weight, WebMD says — and with time, it will go away.

6. Neurontin

A hand holding medication

Neurontin can cause weight gain. | iStock.com/theevening

You may have never heard of Neurontin, which is also known as Gabapentin. It’s a drug used to treat pain and seizures and is also a cause of significant weight gain for many users. Studies have found that some users gained as much as 10% of their body weight with a 3,000-milligram daily dose.

7. Lithobid

pills on blue background

Lithobid can change your metabolism. | iStock.com/BCFC

Lithobid is pretty much what it sounds like — Lithium. It’s used to treat depression and bipolar disorder symptoms, but one common side-effect is change to a person’s metabolism and appetite. As a result, many users gain weight while taking it. That’s only one of a host of reported side effects, however, some of which are far more serious than others.

8. Deltasone

Pink pills

Deltasone can expand your waistline. | iStock.com/agencyby

Deltasone is a medication commonly used to treat issues related to inflammation. This includes arthritis, skin diseases, blood disorders, and even respiratory issues. One of its major side effects is the possibility of weight gain, as with every other item on this list.

9. Zoloft

A bottle of Zoloft

Zoloft also comes with this side effect. | Joe Raedle/Getty Images

Circling back to antidepressants, another popular drug that causes people to put on weight is Zoloft. This particular medication is lumped in the same group of SSRIs as Prozac and Paxil and shares many of the same side effects. One of them, naturally, being weight gain.

10. Insulin

A diabetic checks his blood sugar

Insulin can cause weight gain, too. | iStock.com

Insulin is a hormone used by your body to regulate blood sugar levels. Weight gain and diabetes are closely related, and people who have diabetes take insulin to help manage the disease. Weight gain is a common side effect of taking insulin, as your cells can absorb more sugar (glucose) than needed. That is then stored as fat, causing people to gain weight.