How Soon Can a Blood Test Detect Pregnancy?

Getting Answers as Quickly as Possible

And you thought waiting at the DMV was bad. When you're hoping for a positive result, it's excruciating to wait until you're in the right window of time to take a pregnancy test. Sure, you can use a home testing kit anytime, but the results won't be accurate if you take it too soon. A blood test is the more definitive method for determining pregnancy, and it's how your doctor will confirm that you really are expecting. But while a blood test detects pregnancy a little sooner than a urine test, you'll still have to wait at least several days after having intercourse to find out.

How Does a Blood Test Work?

How Long Do Pregnancy Blood Test Results Take?

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Blood tests and urine tests both work the same way. They detect the presence of human chorionic gonadotropin, or hCG, a hormone that your body starts producing as soon as your fertilized egg implants in your uterus. Once you get pregnant, your hCG level starts rising rapidly, doubling every few days. It must reach a certain point before a urine test can detect the hormone. A urine test uses a treated strip that reacts when it comes in contact with a significant amount of hCG.

Doctors use two types of hCG tests. A qualitative test just tells the doctor if you have hCG in your blood or not, but like urine tests, the hormone level has to reach a certain point before the test can detect it. A quantitative hCG test is more definitive. It measures the exact amount of the hormone in your blood so it may reveal that you're pregnant sooner than a qualitative test or urine test would.

How Quickly Does a Blood Test Work?

Unfortunately, it's impossible to say exactly how quickly after intercourse a blood test can reveal pregnancy. That's because it's impossible to predict exactly how long the conception process will take. Sperm can live in your body for a few days, so it may not fertilize your egg right away. Further, the fertilized egg stays in your fallopian tube for several days before moving into the uterus and implanting there.

A blood test may be able to detect your pregnancy within six days of ovulation, but depending on where you are in your cycle and when you had intercourse, it may take as long as 14 days or more for the test to give you an accurate result.

If you have an embryo transfer or other fertility procedure, the doctor will tell you when to come back for a blood test. Typically you'll have to wait about two weeks in order to get the most accurate result. Taking the test too soon and getting a false negative can be devastating, so it's better to wait until your body has time to produce enough hCG to be detected.

What Happens During a Blood Test?

How Does a Pregnancy Test Work?

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Even if you take a urine test at home and get a positive result, your OB/GYN will probably use a blood test to confirm the results. Alternately, you can bypass the urine test and call your doctor for a blood test if you suspect you may be pregnant.

Your doctor should ask you some questions about your menstrual cycle and recent intercourse to try to establish a timeline. She'll take a small sample of blood and send it to a lab for testing. Some doctors' offices have onsite labs that can test samples quickly. If yours doesn't, you may have to wait a few days for the results to come back. Yes, more waiting—but you'll have your answers soon enough.

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