Take it too soon and your results won’t be accurate.

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Like the Spider-Man saying goes, with great power comes great responsibility. So, yeah, if you’re having sex, you owe it to yourself to understand the early symptoms of pregnancy, how pregnancy tests work, and when you should take one. It’s the smart, safe thing to do.

YOU SHOULD TAKE A PREGNANCY TEST IF…

You’ve had unprotected sex.

Maybe you got swept up in the moment and forgot to use a condom, or maybe you had sex before you scheduled an appointment with your doc to talk about going on the Pill, implanting an IUD, or using another kind of birth control that works for you. Whatever the sitch, unprotected vaginal sex puts you at risk for pregnancy and sexually transmitted infections. Taking a test at the right time (see below) can give you peace of mind, or allow you time to plan for whatever your next steps are in the case of pregnancy.

If you had unprotected sex within the past three to five days, you’re a candidate for a morning-after pill: Plan B is 75 to 89 percent effective if taken within three days (72 hours) and Ella is 85 percent effective if taken within five days (120 hours). FYI: If your BMI is over 25, Ella works better than Plan B.

And remember to get tested for STIs — you can do that at your doctor’s office or at a local clinic, like Planned Parenthood (which is usually free or at a reduced price).

Your method of birth control failed.

It sucks, but it happens — if the condom breaks, you forgot to take the Pill, or you’re on a antibiotic that might affect the results of the Pill, there’s a chance you could get pregnant. In this case, take a pregnancy test (and if the condom broke, you want to get tested for STIs, too). You should also look into a morning-after pill (see directly above for details).

You missed a period (and you’re sexually active).

If your period is usually pretty regular, not getting it is a huge red flag (or, um, missing red flag) that you might be pregnant. Your uterus waits around for a fertilized egg to appear. If it doesn’t appear during the course of a month, your uterus sheds its lining — which comes out of you in the form of period blood. But when a fertilized egg does make it to your uterus, your body’s like, nah, I’ll hold onto the lining this time. No period. If your cycle’s less reliable than a f***boy texting back right away, then keep reading.

Your period is irregular and you have symptoms of early pregnancy.

Some signs to watch out for:

  • a missed period
  • sore or tender breasts
  • cramps
  • nausea
  • aversions to certain foods
  • exhaustion
  • increased urination

Notice anything kinda frustrating? Yeah, half of those — like sore breasts and cramps — are symptoms of PMS, too.

If you’ve had unprotected sex in the past and are worried that pregnancy might be a possibility, take a test just in case. And if you’re not pregnant, take note of what your body feels like so you can be more prepared for PMS in the future.

You used birth control, but you still have symptoms of early pregnancy.

It’s not fair: you make the safe, proactive choice to use BC, and it still leaves you with a sliver of risk for getting pregnant. According to Planned Parenthood, here’s how effective various methods are when used perfectly (i.e. you take the Pill every day at the same time without ever messing up, or you replace your implant as soon as your doctor recommends).

  • Implant (Nexplanon): 99 percent
  • IUD: 99 percent
  • Shot: 94 percent
  • Patch: 91 percent
  • Pill: 91 percent
  • Vaginal ring: 91 percent
  • Condom: 82 percent
  • Withdrawal (pull-out method): 73 percent

The stats are scary but true — even when used flawlessly, BC doesn’t guarantee that you’ll never get pregnant (abstinence is the only way to do that). But one way to up your odds of staying pregnancy-free while sexually active is to double up: using condoms plus another method… which you should be doing with untested partners anyway to prevent the spread of STIs.

You think you’re pregnant.

An obvious but important disclaimer: you know your body better than anyone else on the planet. If you’re worried that something’s up, take a test.

HERE’S WHEN TO TAKE A PREGNANCY TEST FOR THE MOST ACCURATE RESULTS

Annoying newsflash: you can’t just take a test at any old time and expect it to magically tell you if you’re pregnant.

It all comes down to the timing of your cycle. During ovulation, your uterus releases an egg from the ovary into the fallopian tube. If your partner’s sperm finds and fertilizes that egg within 24 hours, it’ll travel to the uterus and implant there within eight to 10 days.

Pregnancy tests measure the level of a hormone called human chorionic gonadotropin (hCG for short) that’s produced by the placenta — in other words, only present in pregnant people. Some super-sensitive home pregnancy tests can detect hCG in your urine eight days after ovulation. But the tests are most accurate and reliable if you wait 12 to 14 days after ovulation, which typically coincides with the date of your first missed period (if your cycle is 28 days long). Any earlier than that, and you risk getting a false negative.

FYI: HERE’S WHERE TO GET PREGNANCY TESTS

Pregnancy tests are available at drugstores, pharmacies, or supercenters like Target and Walmart (check the family planning section, near where condoms are sold — probably in or next to the tampon aisle). You can also buy them online.

Home pregnancy tests are only so accurate, though. A blood test (administered by your doctor, a local health clinic, or Planned Parenthood) can confirm your results; if a home pregnancy test gives you a positive result, you should definitely follow up with a blood test ASAP.

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