It seems that we're a nation of pill-poppers: Nearly 70 percent of Americans take at least one prescription drug, and more than 50 percent take two, according to a 2013 report from the Mayo Clinic. While many of those meds might very well be keeping us healthy, some of the most popular drugs on the market—including prescription and OTC options—can also cause debilitating tiredness. Could your pills be the reason you can't seem to make it through the day without multiple cups of coffee? If you're getting ample sleep but still yawning all the time, one of the following medications might be to blame. (Looking to take back control of your health? Prevention magazine has smart answers—get 2 FREE gifts when you subscribe today.)

Antidepressants

They're among the most commonly prescribed medications, especially for women. (Women are twice as likely as men to take antidepressants, according to the National Center for Health Statistics.) But they can also make you tired, says Nancy Simpkins, MD, a board-certified internist who specializes in women's health and practices in Livingston, NJ.

Most modern antidepressants (SSRIs, or selective serotonin reuptake inhibitors) work by regulating serotonin, a mood chemical in the brain that plays an important role in sleep. Although SSRIs tend to be less sedating than older antidepressants (including tricyclics such as Elavil), some people still end up feeling sluggish. Zoloft users often report this side effect, says Simpkins. (Here are 11 things only someone on antidepressants understands.)
 
With SSRIs, "the first 8 to 10 hours is the most potent part of the dose," Simpkins says. "If a patient is doing well on Zoloft but they're tired, we tell her to take it at night," she says. If you still can't shake that foggy feeling, ask your doctor about trying out a different drug in the same class, such as Paxil, Prozac, or Lexapro.  

Antihistamines

You may be taking them for your seasonal allergies, but these drugs are also really good at helping you doze off—so good, in fact, that they're actually used in sleep aids like Unisom. They work by blocking histamine, an itch- and sneeze-inducing chemical that also happens to be a neurotransmitter. 

"Histamine gives you energy and helps your brain function normally," says Simpkins. "When you block it, you block the allergic reaction, but you're also blocking the normal functioning of the brain." Hence, the sleepiness. 

All antihistamines—even the ones marketed as "non-drowsy"—have the potential to make you sleepy. That said, some are more sedating than others. "The least sedating one tends to be Allegra, followed by Claritin and then Zyrtec," Simpkins says. Benadryl usually causes the most sleepiness, along with a more powerful prescription medication called Xyzal that's sometimes used for treating severe allergies. 

People with bad allergies have a few options: Try taking Benadryl or Xyzal before bed, or switch to a less drowsy option. (Simpkins likes Zyrtec the best.) "If you're really miserable, get allergy shots," she says. (Never take these 5 over-the-counter medicines together.)

Blood pressure medication

According to the CDC, nearly 75 million Americans—a staggering 1 in every 3 adults—suffer from hypertension. It's often treated with beta blockers, but these drugs aren't exactly well-liked among patients. When people take them, says Simpkins, "they really complain. Some say that they feel like they have the flu."

Beta blockers inhibit the production of adrenaline, a hormone that causes your heart to beat rapidly. By slowing your heart rate, they lower the force of the blood pounding on your artery walls (aka your blood pressure). But having less adrenaline can also zap your energy level. One beta blocker, Inderal, is particularly fatiguing, says Simpkins.  (These 13 power foods can help lower your blood pressure naturally.)

The fix? "You can lower the dose a little, and some people feel better," says Simpkins (be sure to get your doctor's OK before changing your dose). If that doesn't do the trick—or your blood pressure isn't being well-controlled with the lower dose—ask your doctor about switching to an ACE inhibitor, which works differently: ACE inhibitors dilate your vessels so that blood can flow through them more efficiently, and they shouldn't make you tired.

Anti-anxiety medications

Benzodiazepines are among "the most widely prescribed medication in the world," says Simpkins. "And all of them cause fatigue."

These drugs bind to a receptor in the brain that releases a chemical called GABA. When GABA is released, it signals the brain and body to relax, which can provide short-term relief to someone with intense anxiety. But it may also work a little too well, causing you to become drowsy or even fall asleep.

Xanax is the least sedating of the benzodiazepines, says Simpkins, and thanks to a short half-life, only works for a few hours. "I prescribe a small dose to patients who need an MRI but are too afraid of going in the machine," she says. "Most people are able to drive to the test and drive home after."

The most sedating drug in this class is Ativan, says Simpkins. It causes so much sleepiness that doctors typically prescribe it as a sleep aid for people whose anxious thoughts are keeping them awake.

If you need anti-anxiety medications at a time when you can't afford to be sleepy—perhaps you're prepping for an important work presentation rather than settling in for a long flight—Simpkins recommends experimenting: "I tell patients to take the lowest dose of Klonopin or Valium and cut it into quarters. "The first quarter is basically a placebo effect, since there's not enough medication to be a therapeutic dose. But for some people, that's enough. If you still feel anxious after 15 or 20 minutes, take another quarter." (Maybe it’s not the med; here are 7 more reasons you're tired all the time.)

This article originally appeared on Prevention.com.