All early pregnancy tests are the same in that they look for a special hormone in either the blood or urine that is only present when a woman is pregnant. This specific hormone is called human chronic gonadotropin (hCG), or more commonly referred to as the pregnancy hormone.
Two different types of early pregnancy tests are available, urine and blood tests. Both tests will look for the pregnancy hormone, hCG. In today's world, many women use the urine test, or home pregnancy test (HPT), to discover whether they are pregnant or not. The best features of HPT's are that they don't cost a lot of money, they are easy to use, can be completed at home, and are completely private for the woman.
The two blood tests for early pregnancy tests are performed by a health care provider. The first early pregnancy test is referred to a quantitative blood test. It measures the exact amount of hCG in the blood. This test can pick up very small amounts of hCG, making it a highly accurate test. The second early pregnancy test is called a qualitative hCG blood test. It gives a simple yes or no answer for the question of a pregnancy. This test is more like the urine test in regards to accuracy.
Early pregnancy tests such as the blood test can pick up hCG much earlier in a pregnancy than urine tests can. A blood test can pick up the pregnancy hormone about 6 to 8 days after ovulation. The best accuracy time for the urine test is 2 weeks after ovulation. Some of the ultra sensitive urine tests can determine pregnancy as early as 6 days after conception, or one day after a missed period.
Most early pregnancy home tests are very accurate. Depending on the use, a home pregnancy test will be 97% to 99% accurate. If an early pregnancy test is not done correctly at home, the test will be less accurate.
If an early pregnancy test is done too early, there may not be enough of the pregnancy hormone in the urine to have a positive test result. Most early pregnancy tests will be accurate if the test is done around the time the next period is due. Most medications, including both over the counter and prescription drugs, should not affect the results of an early pregnancy test.