What is the difference between blood and urine pregnancy tests?

All pregnancy tests test for the presence of the pregnancy hormone, HCG (human chorionic gonadotrophin); this hormone is secreted from the developing placenta in the event of an egg being fertilised. HCG plays an important role in preparing the body for pregnancy and also stops periods. If you are pregnant, the hormone will be detected in both your urine and bloodstream.

There are two main types of pregnancy test; those that test the urine and those that test the blood. All home pregnancy tests test urine, while health professionals use blood tests. Most women carry out a home urine test before they go to their doctor for a blood test.

Home urine tests are most effective around one week after a missed period; some people may be able to get an accurate result before this time but research has shown that results are more accurate later on as the concentration of HCG in the urine is higher.

Blood tests can determine results earlier than urine tests; doctors can use either qualitative or quantitative tests. Qualitative tests give a simple yes or no answer, while quantitative tests (also known as the beta HGC test) can determine the levels of HCG in the blood and can consequently tell you how far along you are in your pregnancy. Blood tests can usually give an accurate result around one week after ovulation. Blood tests are usually carried out in the GP surgery; the sample is then sent off to a laboratory and the results are returned to your doctor.

Blood Pregnancy Tests

What is a blood pregnancy test?

A blood pregnancy test is used to determine whether or not a woman is pregnant. The blood test is used by doctors and is usually carried out in the doctor’s surgery or in a health clinic or hospital. The test works by detecting the presence of the pregnancy hormone human chorionic gonadotrophin in the blood. This hormone is secreted by the placenta when an egg becomes fertilised; its role is to prepare the body for pregnancy. The detection of the hormone in the blood is an indicator that a woman is pregnant.

There are two types of blood test; qualitative tests and quantitative tests.

• Qualitative tests: qualitative tests give a simple yes or no answer by testing to see if the HCG hormone is present in the blood.
• Quantitative tests: quantitative HCG tests measure the amount of HCG in the blood, which can give an indication of how far along in the pregnancy a woman is.

How is the test performed?

A pregnancy blood test is done in the same way as normal blood tests; the doctor will insert a needle into a vein in the forearm and draw out a sample of blood. The sample will then be sent away to the laboratory to be tested to see if HCG is present or not; if it is a quantitative test the amount of HCG will also be measured.

Is the test painful?

Blood tests may be a bit scary for some people, especially those who have a fear of needles but the test should be over quickly and you should experience relatively little discomfort. You will have to have a series of blood tests throughout your pregnancy so unfortunately it’s something you’ll have to get used to, but if you are very nervous your doctor will try their best to put your mind at ease.

Is a blood test more accurate than a urine test?

Blood tests are more accurate than urine tests and they can determine results earlier than urine tests. Urine tests are now very accurate but doctors still prefer to use blood tests as they have an even greater accuracy record.

What are the advantages and disadvantages of a blood test?

The main advantages of having a blood test are greater accuracy and the ability to determine how much HCG is present in the blood and therefore get an idea of how old the foetus is. The main disadvantages of blood tests are that the results take longer to come through and it can be a little painful and scary for those who don’t like needles.

Can a blood test ever be wrong?

It is very rare for a blood test to be wrong but it is possible; in most cases, blood tests indicate a false negative result if the test is done too early and a false positive result if the woman has been taking fertility medication, which causes HCG to be present in the blood, or if the woman has had an abortion, a miscarriage or an ectopic pregnancy; it takes a while for the hormone to disappear.

Will medication, drugs or alcohol affect the result of the test?

In the vast majority of cases, medication, drugs and alcohol will not affect the result of the pregnancy test, as the test is only testing for the presence of the HCG hormone. It may be possible that fertility medication may produce a false positive result, as these drugs cause HCG to be present in the blood.

Urine Pregnancy Tests

What is a urine pregnancy test?

A urine pregnancy test is a test that uses a urine sample to determine whether or not a woman is pregnant. The test detects the presence of the pregnancy hormone human chorionic gonadotrophin in the urine. The HCG hormone is secreted by the placenta in the event of an egg being fertilised; if a woman has HCG in her urine, this indicates that she is probably pregnant.

How is the test performed?

Urine tests are usually performed at home; there are different types of test but most require the user to place the test stick under the stream of urine for approximately five seconds. Some tests come with a disposable cup so you can urinate into the cup and then use a test strip to check for the presence of HCG in the urine. Once you have done the test you have to wait for the results to appear; different tests take different amounts of time, so you should read the instructions carefully to see how long you need to wait.

The instructions will also tell you which signs or symbols you need to look out for to see whether or not you are pregnant.

Where can I take a urine test?

Home pregnancy tests can be used anywhere, unlike blood tests which have to be carried out at a doctor’s surgery or in a hospital. You may prefer to do the test at home or in a private toilet, rather than a public toilet as other people may be around but this is down to personal preference.

How many tests should I take?

It is always advisable to take at least two tests; if you get a positive result it is almost certain that you are pregnant but if you get a negative result this may not be so reliable. You should do another test a couple of days after the first test to confirm the result; if you do a test early on and it comes back as negative, it may be that your levels of HCG aren’t high enough for the test to detect; trying again a few days later could give you a different result as levels of HCG will have increased by then if you are pregnant. Many companies now sell double or triple packs of pregnancy tests, which are better value for money and allow you to test more than once.

When should I do a test?

Some tests can be done before your next period is due but most tests are accurate from the day of your missed period. Accuracy usually increases after your missed period as the levels of HCG in the urine will have increased.

It is advisable to do a urine test in the morning as this is when the urine is most concentrated; avoid drinking lots of fluid before taking the test as this could affect the result.

Are urine tests accurate?

Home urine tests are now very accurate but there is a chance that you may get a false negative or false positive result. Most tests claim to be around 99% accurate after the first day of a missed period; tests that are done before your period is due are less accurate as HCG levels are sometimes too low for the test to detect.

How much are home urine tests?

The cost of home pregnancy tests varies according to which brand or type you go for but as a general guide you can expect to pay between £3 and £10. Pregnancy tests are available free of charge from GP surgeries, family planning clinics and sexual health clinics.