Can you take Plan b on birth control? How to use these hormonal medications for max protection

• You should only take Plan B if you've had sex and missed more than three birth control pills.
• You can resume taking your birth control the same day that you take plan B.

Although birth control is very effective at preventing unwanted pregnancies, small mistakes like not taking your pill at the same time each day can increase your risk. In this situation, you may need emergency contraception, like Plan B.

You can safely take Plan B while taking birth control, says Dr. Nicole Mitchell, an OB-GYN with Keck Medicine of USC. But there are careful steps you should take to make sure you are fully protected from pregnancy.

When do I take Plan B if I'm on birth control?

If you've been taking your birth control as directed and not missing doses, there is no need to take Plan B, says Dr. Sophia Yen, a reproductive health expert and the co-founder of women's telehealth provider Pandia Health.

In these cases, the birth control already protects you from pregnancy. Yen says taking Plan B would just give your body more hormones than necessary. This could trigger unpleasant side effects like nausea, pelvic pain, or even vomiting in rarer cases.

However, if you have missed three or more days of birth control, you should use emergency contraception, Yen says.

Plan B is 95% effective at preventing pregnancy if you take it within 24 hours of semen entering the vagina. You can take it up to 72 hours after sex, but the efficacy decreases each day.

Can I continue my birth control pack after I've taken Plan B?

If you're taking Plan B because you missed a few doses of birth control and had unprotected sex, you can continue taking your pills right away. Ideally, you should resume your pack the same day, and avoid sex or use a backup method of birth control like condoms for seven days, Mitchell says.

This is because Plan B only protects you after one incident of unprotected sex, so you'll want to cover yourself while your main birth control method kicks back in.

But there is no one-size-fits-all rule of thumb to be followed. Ultimately, guidelines may vary based on the specific brand of pill you take, so you should look for information based on the specific type of birth control, or even better, contact your OB-GYN for help — particularly if you've missed three or more pills.

Can I take ella on birth control?

Some people may opt for ella, which is a prescription-only form of emergency contraception that's even more effective than Plan B, with only nine out of 1000 people getting pregnant who take it within 24 hours.

Additionally, ella is more effective than Plan B if you weigh over 155 pounds.

But if you opt for ella instead of Plan B, you have to stop your birth control for five days after taking it, says Yen. This is because ulipristal acetate, the active ingredient of ella, is an anti-progesterone.

If you mix this with your hormonal birth control (which contains synthetic progesterone) it defeats the purpose, making the emergency contraceptive less effective, Yen says.

Since you shouldn't take ella and birth control at the same time, you need to use backup birth control such as condoms if you're sexually active during this time period.

Once the five days have passed, it's best to start a fresh pack of birth control after taking ella, Yen says.

What to expect after taking Plan B or ella while on birth control

If you take birth control and Plan B, one of the most common occurrences to expect is your period being off-cycle, as it may come earlier or later than expected, Yen says. This could range from a couple of days to a week away from your period's expected arrival date.

Mitchell says a few other potential side effects of Plan B are:

• Breast tenderness
• Dizziness
• Headache
• Fatigue
• Nausea
• Vomiting

The side effects of ella are essentially the same. However, unlike Plan B, ella may cause menstrual pain, but not breast tenderness.

Insider's takeaway

If you miss multiple days of your hormonal birth control and want to prevent pregnancy after unprotected sex, emergency contraception is a good option.

You can safely take Plan B and its generic forms alongside your birth control. However, if you take ella, you will need to stop your birth control for at least five days after.

If you aren't sure what the best course of action is for you, don't hesitate to call your OB-GYN for advice.