If you take birth control pills, you don’t want to take the chance that your pills are ineffective. Do birth control pills expire? If so, do they still work? Read on to find out.

Birth control pills are a form of hormonal birth control. They’re available as either combination pills or minipills. Combination pills contain the hormones estrogen and progestin. Minipills contain progestin only.

Combination pills work to prevent pregnancy in three ways. First, the hormones stop ovulation from occurring. Second, they thicken the cervical mucus to prevent sperm from traveling to an egg if one is released. Lastly, they thin the lining of the uterus to help prevent implantation.

The progestin found in the minipill functions in a similar way. This hormone also stops ovulation and thickens cervical mucus to prevent sperm from reaching an egg.

The expiration date on any medication helps determine whether the product is safe and effective. Using expired medication is risky and may be harmful.

When a medication expires, it may not be as potent. The medication’s chemical composition may also change. At this point, manufacturers can no longer guarantee that the drug isn’t deteriorating. Because of this, taking expired birth control pills may result in an unwanted pregnancy.

The U.S. Food and Drug Administration requires manufacturers to list an expiration date on the packaging for all medications. The date may be printed on the label or stamped on the pill container. If a month is listed but not a year, it’s understood that the pills expire on the last day of that month. For example, if you have a pack of pills that expire in May of the current year, you can still take these pills during that month. You wouldn’t want to take this pack anytime after that month, though.

Read more: Which birth control is right for you? »

You should dispose of expired birth control pills properly. Most medication package inserts have disposal instructions, or you can check to see if there’s a drug take-back program in your area. Be aware that most pharmacies won’t exchange expired pill packs for new ones.

If you choose to dispose of expired pills in the trash, the FDA suggests these disposal guidelines:

  1. Mix pills with an unpalatable substance such as cat litter, used coffee grounds, or dirt.
  2. Put the mixture in a sealed container or plastic bag.
  3. Throw the container away.

If you take expired birth control pills, your risk of pregnancy increases. If you discover that your pills have expired, use a backup birth control method such as condoms until you can start a new pill pack.

It can be easy to let birth control pills expire without even realizing it. If you receive more than one month’s supply at a time, be sure to use the oldest pack first. You can also maximize your pill’s effectiveness by taking it at the same time every day.

Birth control pills are up to 99 percent effective when taken at the same time every day without missing a dose. This is considered “perfect use.” If you miss a dose or take the pill at a different time each day, the pill is about 91 percent effective. This is considered “typical use.”

Combination birth control pills are available in 21- or 28-day packs. In both types of packs, there are 21 pills that contain hormones. In the case of 28-day packs, there are seven “reminder pills” that don’t contain hormones.

When taking 21-day packs, one pill is taken every day around the same time for three weeks. The following week no pills are taken, and the week after that you start a new pack.

Twenty-eight day packs are taken the same way, but you take the seven inactive pills the last week. If you skip this week of inactive pills, you may forget to start your new pack on time. This can affect the level of hormones present in your body and may affect your birth control’s effectiveness.

Progestin-only pills come in 28-day packs. All pills contain progestin and are taken once daily around the same time. There are no placebo pills in a progestin-only pill pack.

If you think you’ll have difficulty remembering to take a daily pill or you’re concerned about pills expiring, you may want to consider other birth control options. Other forms of reversible birth control include diaphragms, intrauterine devices (IUDs), and patches. Permanent forms of birth control include vasectomy for men and tubal ligation for women.

When choosing birth control, you should consider:

  • whether it contains any hormones
  • it’s effectiveness
  • it’s cost
  • it’s availability
  • how soon you wish to become pregnant

Like all medications, birth control pills expire. Taking expired pills may result in an unplanned pregnancy, so why take the risk? You should always check the expiration date on your pills before you begin using them. If you have questions or concerns, your doctor or pharmacist may be able to assist you.