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Blood Pregnancy Test: What it is and How it Works

Women who have already conceived find out they are pregnant by conducting urine-based home pregnancy test. Sometimes, the doctors ask to conduct a blood pregnancy test too. There are cases when a blood test may be preferable though a urine test is all you require. Here we explain what a blood pregnancy test actually is and how it is different from a urine test.

A blood pregnancy test is quantitative blood test that shows the amount of human chrionic gonadotropin (hCG) in the blood. This test is referred by most people when they need to conduct pregnancy blood tests in London. In order to test your blood for hCG, the blood sample will be taken from your veins which can be in the arm, through a process known as venipuncture.  

HCG is a hormone secreted during pregnancy which can be detected in one to two weeks after you conceive based on the test.When you perforn home pregnancy test that uses blood or urine pregnancy test, the results depend on the measurements of this hormone in your urine or blood.

Difference between urine hCG test and blood hCG test

A blood pregnancy test is very sensitive when compared to a urine pregnancy test. Most blood tests may detect somewhat lower amounts of hCG which means they can tell whether you had been pregnant a few days before. The urine tests require slightly more hCG for showing positive results. This makes false-negative results more likely with urine tests.

Urine hCG test

  • Requires somewhat more hCG for positive reading
  • Tells whether or not you are pregnant
  • Qualitative test
  • Can be accurate a few days to one week after your missed period

Blood hCG test

  • Slightly more sensitive in comparison to urine tests
  • Track hCG levels over time
  • Can be quantitative or qualitative
  • May be accurate before your missed period

Qualitative tests

Urine tests are qualitative which means they may either detect hCG in your blood by providing positive reading or they don’t which means negative reading. You may need to conduct qualitative blood hCG test fr calculating hCG in your blood. The results are clear which means you are pregnant because there is the presence of hCG in your blood or you are not pregnant because there wasn’t hCG in the blood.

How soon a blood test can detect pregnancy

Blood pregnancy tests may pick up hCG in the blood for six to eight days before ovulation. Urine pregnancy tests may detect pregnancy within10 days after conception. It is advisable to wait for one week after your missed period before conducting a urine pregnancy test for ensuring optimal efficacy.

Quantitative tests

Another option is getting quantitative hCG blood test which provide your doctor more information whether or not you are pregnant. These tests may select small amount of the hormone and calculate exactly the amount of hCG present in the blood, Your hCG levels will almost get double in every two days during the early pregnancy.

By having several blood tests within 48 hours, the doctor will be able to track your hCG levels and get better reading on your pregnancy. These private pregnancy blood tests help the provider to monitor your pregnancy for ectopic pregnancy or miscarriage and the chances you are carrying multiples in the womb.

When a blood test can be used

During regular pregnancies with healthy women, at-home urine tests are more effective. Blood tests help to detect where there is any potential issue with your pregnancy or other complications.

The private pregnancy blood tests in London are done to denote higher risk pregnancies at the time of fertility treatments when urine tests are negative but you have missed a period. This will confirm or rule out possible miscarriages or multiples and diagnose probable tubal or ectopic pregnancy due to other pregnancy complications.

Urine versus blood pregnancy test

Urine tests are easy to use, and painless which can be done at a low price in the privacy of your home. This is considered to be the standard test for most pregnancies.

A blood pregnancy test is very accurate which provide instant results that can give the doctors detailed information about your pregnancy.

Higher hCG then expected

When you have higher than normal hCG level, this can denote:

  • Infection or malignant tumors of your uterus
  • Non-cancerous tumors of uterus
  • More than one fetus which can be twins or triplets
  • Testicular cancer in men
  • Ovarian cancer
  • Denote normal pregnancy

Lower hCG than expected

If you are having lower than normal levels of hCG, this may mean:

  • Ectopic pregnancy
  • Probable death of your fetus
  • Incomplete or complete miscarriage


There is minimal risk involved with blood pregnancy test. Other than minor pain on injecting the needle, most people do not have other side effects from drawing blood. Some people will have bruising occasionally at the injection site. There are rare cases when some people have infection, excessive bleeding, or fainting after drawing blood. You should tell the doctor know if you ever have had an issue with getting blood drawn at the time of conducting private blood tests in London

In case of most women, a urine-based or at-home pregnancy test will be more than enough to confirm the chances of pregnancy. Sometimes conducting a blood pregnancy test, either quantitative or qualitative type, is required to give more information, particularly in medically complicated conditions. Both these tests are effective ways to know whether you are pregnant.