What is a pregnancy test for blood, and how does it work?

By taking a urine-based home pregnancy test, most pregnant women find out that they are pregnant. Doctors also recommend you take a blood pregnancy test too. In rare circumstances, there are several explanations why a blood test might be preferred, but generally, a urine test is all you need. Below, we explain precisely what a test is for blood pregnancy and how it varies from a test for semen.

Typically, a blood pregnancy test is a quantitative blood test showing the amount of human chorionic gonadotropin (hCG) in your blood. This is the sort of blood pregnancy test referred to by most people when they talk about pregnancy blood tests. A simple blood sample is obtained from one of your veins, usually in the arm, through a process called a venipuncture, to test your blood for hCG.

Depending on the test, HCG is a hormone secreted in pregnancy and detectable from a week to two weeks (or more) after conception. The results will be based on tests of this hormone in your semen or blood, whether you are using a home pregnancy test that uses urine or a blood pregnancy test from your doctor. When used correctly, both types of tests are very accurate, providing around 99 percent accuracy.

16 Myths to Get Pregnant

What is the difference here?

A blood test for pregnancy is more reliable than a test for urine and can provide more detail. Many blood tests can detect slightly lower levels of hCG, so if you're pregnant a few days ago, they can tell you. Urine tests appear to require slightly more hCG to read positive, with urine tests making false-negative results a little more likely, although overall rates are very low.

• Needs slightly more hCG to read positively

• Qualitative Testing Test

• Don't tell you how much hCG is in your blood whether you are pregnant or not.

• A few days to a week after a missed time is reliable.

• Slightly more sensitive than studies on urine

• Qualitative or quantitative may be

• Can time-track hCG levels

• Before a missing time, may be accurate

Qualitative Testing Tests

Urine tests are qualitative, meaning either they detect hCG in your blood, or they don't give a positive reading, which is a negative reading. To measure hCG in your blood, you can also have a qualitative blood hCG test. Again, the findings are very clear: yes, because we found hCG in your blood, you are pregnant, or, no, because we didn't find it, you are not pregnant.

Urine pregnancy tests will typically detect pregnancy within approximately 10 days of conception. Blood pregnancy tests six to eight days after ovulation will pick up hCG in the blood.

For optimum effectiveness, it is recommended to wait a week (or at least a few days) after a missed time before taking a urine pregnancy test.

Tests for Quantitative

A quantitative hCG blood test is another alternative (also called the beta hCG test). These tests will provide more detail to your doctor or midwife than just whether or not you're pregnant. Very small quantities of the hormone can be picked up by quantitative hCG tests to measure exactly how much hCG is in your blood. It's important to compare this knowledge over time.

In general, in early pregnancy, the hCG levels will nearly double about every two days.

Your doctor will monitor your hCG levels by doing several blood tests about 48 hours apart to get a better reading of your pregnancy, if needed. These serial blood tests will help track your pregnancy for miscarriage or ectopic pregnancy by your physician, as well as the risk that you carry multiples.

These tests are not conducted routinely (or required) for every pregnant woman due to stress, cost, and other factors. If you agree that a blood test for pregnancy is correct for you, talk to your doctor or midwife. You should be able to depend instead on the results of your home pregnancy tests (HPT) if your unique circumstances do not warrant a blood test.

Signs with multiples, you're pregnant

When Use a Blood Test

At-home urine tests are more than adequate and reliable in regular pregnancies of healthy mothers. Blood tests are mostly used in the offices of doctors, especially if there is a possible concern with pregnancy or some other complicating factor (such as multiples) that needs higher blood test sensitivity.

During fertility treatments, when urine tests read negative but a period has not come, blood tests may be ordered for higher risk pregnancies to confirm or rule out a possible miscarriage or multiples, and to diagnose a potential ectopic or tubal pregnancy, as well as because of other complications of pregnancy.

Urine Effectiveness vs. Blood Pregnancy Tests

Urine tests are low-cost, painless, easy-to-use, can be conducted in the privacy of one's home, and are very precise (in most scenarios), which is why most pregnancies are the standard examination.

On account of complicating factors, a blood pregnancy test is warranted. These tests are also very specific, offering fast results that can provide more accurate details about your pregnancy to doctors.

Interpreting results

Standard findings from a quantitative hCG blood pregnancy test will suggest that during the first trimester of pregnancy, hCG levels increase steadily and then decrease marginally after about 10 weeks. The hCG levels stabilize for the duration of the pregnancy at about 16 weeks. On the other hand, irregular findings can mean a number of things.

Lower hCG than was expected

• Infection or uterine malignant tumors

• Over a single fetus (for example, twins or triplets)

• Non-cancerous uterus tumors

• Cancer of the ovaries

• Often, just a sign of a normal pregnancy, in childbirth, farther along

• Cancer of the testicles (in men)

Lower hCG than was expected

• Pregnancy of ectopics

• Miscarriage partial or complete

• Possible Fetus Death

Understanding the risks of miscarriage and its causes

A blood pregnancy test is associated with very little risk. Most people do not have any other side effects from getting blood drawn, aside from mild discomfort when the needle is injected. Some individuals may occasionally have bruising at the site of the injection.

Some individuals suffer excessive bleeding, fainting, or infection from getting blood drawn in rare cases. Let your doctor know if you have ever had a blood-drawing problem.

A urine-based, at-home pregnancy test would be more than enough to confirm pregnancy for most women. In order to provide more detail, particularly in medically complex circumstances, a blood pregnancy test, either qualitative or quantitative, is sometimes required. Both tests are safe, simple, and successful ways to decide if you are pregnant. Blood checks are best because there might be something else going on.

Are pregnancy tests for blood safer than home testing?