Blood tests are done in a doctor's office. They can pick up hCG earlier in a pregnancy than urine tests can. Blood tests can tell if you are pregnant about six to eight days after you ovulate. Doctors use two types of blood tests to check for pregnancy: 
•    Quantitative blood test (or the beta hCG test) measures the exact amount of hCG in your blood. So it can find even tiny amounts of hCG. This makes it very accurate. 
•    Qualitative hCG blood tests just check to see if the pregnancy hormone is present or not. So it gives a yes or no answer. This blood test is about as accurate as a urine test.