Deciding when to take a pregnancy test can be a little nerve wracking. You may feel especially stressed or confused if it’s your first time being tested. Don’t worry: Once you’re dating, the process becomes a lot less intimidating.

It all starts with peeing on a stick or in a cup: home pregnancy tests check your urine for a hormone called human chorionic gonadotropin (HCG). Tests usually claim to be 99% accurate when used correctly. But for results you can trust, it is crucial that you slim on time.

First, a little 101: After your embryo moves into your uterus (during implantation), the cells that will eventually become your placenta begin to produce and secrete HCG. Pregnancy amounts completely increase and enter your bloodstream – and your pee. But HCG levels take time to rise high enough for a pregnancy test to detect.

So when should you mark your calendar for that solo bath? Here’s what the pros recommend.

How long should you wait to take a pregnancy test?

Experts usually say to wait until you miss your period (often around 14 days after conception) or even a few days after that.

Do your best to wait until the time of the missed period to download the test to avoid unnecessary disappointment.

– MD Shannon Smith, OB-Gyn at Brigham Faulkner OB/Gyn Associates

While you might have enough hCG in your urine a week or so after conception — and some pregnancy test manufacturers claim to deliver accurate readings around this time — the hormone levels may not be concentrated enough for a positive result if you are, indeed, pregnant.

During the first few weeks of pregnancy, HCG usually doubles every two to three days (although a slower rise may still be normal). So waiting just a few days can make the difference between an accurate result and a false one.

Dealing with irregular periods can make this one tricky. If you are not sure when your next period will start, try these as benchmarks for the test instead: Counting 36 days from the start of your last menstrual cycle or four weeks from the day you had unprotected sex.

The best time of day to delay a pregnancy test

Good news for early birds: You pee in the morning, so it’s smart to take a pregnancy test right after you wake up. Don’t drink water or other beverages before you go – fluids can dilute the amount of HCG in your urine.

If you’re in a rush — or not ready for a rollercoaster of emotions before you start your day — we get it. If you plan to take the test later, avoid swallowing large amounts of fluids or using the bathroom for at least three hours beforehand. This will help make your urine more concentrated (it should be a slightly darker color than the typical pale yellow) and give the test a better chance of picking up the HCG.

Are some pregnancy tests more accurate than others?

Yes, some tests are more sensitive than others. (Here are some favorite pregnancy tests.) Check the package and test instructions to understand how early it can detect a positive pregnancy.

But remember, no matter how sensitive the test requirements, you’ll get the most accurate results if you wait to test until after your ghost period. Like Community for bebeCenter Member BcLary1124 put it, “I don’t like testing early because it’s just ‘bleh’ feeling the negatives. I’d rather wait until it’s definitely safe after a missed period.”

“The earlier you try to test, the greater the chance of a false negative — meaning the test says you’re not pregnant when you are,” says Shannon Smith, MD. Gyn at Brigham Faulkner OB/Gyn Associates and member of the Medical Advisory Board for bebeCenter.

Testing too early is actually the most common mistake Dr. Smith sees his patients. If you’re hoping to get pregnant, she advises, “Do your best to wait until after your missed period to take the test and avoid unnecessary disappointment.”

Your healthcare provider may also order a pregnancy blood test, which measures HCG in your bloodstream. A sample is usually collected from a vein in your arm in their office or hospital and sent to a laboratory for analysis.

Pregnancy blood tests can pick up much smaller amounts of hormones and catch your pregnancy earlier. Blood HCG can be detected as early as six to eight days after ovulation (or about 6 to 8 days before your period starts, depending on how long these cycles usually are).

This route is not common because blood tests are more expensive and results take longer. But your provider may recommend one if they want a closer look at the HCG level, if you have a history of ectopic pregnancy or miscarriage, if your urine test results are unclear, or if you’ve experienced any menstrual bleeding with a positive home test.

Should I take another home pregnancy test?

Yes – there’s a good reason many pregnancy tests come in packs of two or three. To be sure of your results, wait a few days and take another test, ideally a few days after your expected period.

Again, a negative result does not necessarily mean that you are no Pregnant. You may have tested too early, or you may have ovulated later than you thought and are not far enough along for the test to be effective. It’s also possible that you didn’t follow the instructions exactly – hey, it happens! – or drank a lot of water and diluted the urine. (For more on common mistakes, here’s what not to do before taking a pregnancy test.)

After you take another test

• If you get another negative result And I still haven’t gotten my period, call your provider. They may recommend a visit to check things out.
• If you get a positive resultcall your provider. They will likely recommend a blood test or ultrasound to confirm the pregnancy. (Note that if you are taking fertility drugs, false positives can happen, so the results may need to be confirmed by your doctor. A chemical pregnancy can also trigger a false positive.)
• If you Get mixed results – Say, a few negatives followed by a positive or vice versa – call your service provider. You may need an ultrasound as a next step.

Bottom line: Getting comfortable with home pregnancy tests takes some trial and error. But the sooner you know you’re expecting, the sooner you can consider all your options and decide what’s next. And if you’re already curious, use our due date calculator to find an estimated due date. Trust us, time will fly!