Whether you want to know the second you’re pregnant or you’re just trying to be efficient and cost-conscious, it’s critical to know when to take a pregnancy test. Using an at-home kit at the right time (and not before) can also help you avoid false hope— or premature worry, depending on your circumstances. Here’s how to choose the best time for the test, along with advice on the next steps

How the stick test works

The very earliest stage of pregnancy is when the egg fertilized by a sperm attaches to the uterine lining and the placenta starts to form. That makes the woman’s body begin to produce “human chorionic gonadotropin,” or HCG, a hormone that enters the bloodstream and urine. Home pregnancy tests work by measuring how much HCG is in a woman’s urine.

To use a kit, you’ll either hold the test stick in range of your urine stream or capture your urine in a cup and then use an eyedropper to convey several drops onto a chemically-treated strip. Afterward, you wait a designated period of time. Depending on which kit you buy, a color change, the presence of one or two lines or a plus or minus symbol tell you if you’re pregnant. Clearblue also sells a pregnancy test that shows either the words “not pregnant” or “pregnant” in the window.

The best time to take the test

If your most pressing question is, “When can I take a pregnancy test?” you are probably anxious for the results. Some OTC pregnancy tests say they can give results a few days before your missed period and you can certainly try then if you like. But for the most accurate results, wait at least until the first day after you miss a period. The reason that’s the best time to take a pregnancy test is that HCG concentrations can double every two days in early pregnancy, so waiting even a few days can make HCG levels easier to detect.

Should you know precisely when you had unprotected sex, take the test 21 days after that. That will help you avoid waiting to miss a period, particularly if you have irregular periods. And keep in mind that ovulation can switch up its schedule month to month and a fertilized egg can implant in the uterus on a varied timetable. When you’re able to take the test based on how many days it’s been since you could have conceived is your safest bet. Also, if you take the test and the results indicate you’re not pregnant, it’s best to wait a few days or a week and take the test again. After that, if you’re still testing negative but having other early symptoms of pregnancy, be safe But if If you have a negative test but think you might be pregnant, like fatigue, breast tenderness or nausea, see your health care provider and get some answers.

Can you trust the results?

If you follow the instructions to the letter and use a kit that’s not expired, pregnancy tests work 99 times out of 100. User error is the most likely cause when a test doesn’t give accurate results. The top mistake to avoid is not knowing when to take the pregnancy test and so taking it too early. You can also mess up by checking the results before the test has had time to work. Some women also neglect to follow the instruction that says to test using urine from first thing in the morning. If you take the test later in the day, your urine has time to dilute and the HCG levels will not be as strong and may not show up on the results.

Find a free pregnancy test

It’s pretty simple to purchase a pregnancy test privately from a drugstore, big box store like Walmart or at some convenience stores. They aren’t super expensive, usually costing around $9-$15 for brand names or multi-packs. Some dollar stores also carry pregnancy tests that cost as little as $1 and many store-brand kits start at about $4. It’s also possible to get a pregnancy test at a doctor, community clinic or local Planned Parenthood Health Center, but they will usually just be using the same test you can do at home. Some Planned Parenthood clinics offer donations-based tests and they’ll keep your identity confidential if you call your local center to determine their payment procedures.

Certain health centers also offer a free pregnancy test. If you’re thinking about using the services of a crisis pregnancy center, be careful to do a little research ahead of time. While they do typically offer a free pregnancy test, they aren’t usually staffed by medical professionals, nor can they offer you medical information about pregnancy options.

Is a blood test necessary?

A pregnancy blood test is another option completed at a clinic or OB/GYN. It also measures the presence of the HCG hormone, but in the blood, not the urine. It’s more expensive than an OTC pregnancy test and adds the cost of a doctor visit. But the blood test may be able to detect pregnancy as early as 7-12 days from possible conception, so it’s a necessity when a potential pregnancy is high-risk or the result of a crime. It’s also a good option if you’ve taken multiple home pregnancy tests and gotten mixed results. Many doctors also use a blood test to confirm a pregnancy after a woman has a positive result from a home test, The levels of HCG in the blood help an obstetrician or registered nurse midwife track and prevent some pregnancy complications.