Quantitative hCG blood tests measure the levels of hCG in a woman's blood. When doctors order these tests, they usually order at least two separate blood draws over a period of two to three days.
Levels of hCG in the blood can vary heavily, and a wide range of levels can be considered normal in early pregnancy. One hCG measurement usually does not provide much helpful information for women with miscarriage symptoms; you need at least two tests to check whether the level is increasing or decreasing.
In early pregnancy, doctors usually use two consecutive hCG blood tests about two to three days apart to check whether the hCG level is increasing or decreasing. In 85% of normal pregnancies, the hCG level should double every two to three days in the early weeks of pregnancy.
Slow-rising hCG levels can be a sign of pregnancy complications, but not necessarily -- if 85% of normal pregnancies have hCG levels that double every two to three days, that means that 15% of normal pregnancies might have slower doubling times.
The answer depends. One low hCG level does not necessarily mean much, especially if the low hCG level was in the first few weeks of pregnancy. Doctors really need two hCG results to determine whether an hCG level indicates miscarriage. The main indicator is whether the hCG level is going up significantly or not.
When hCG levels fall over time during the first trimester, this usually does mean an impending miscarriage.
Your water intake should not affect the concentration of hCG in your blood, but drinking a lot of water could affect the accuracy of urine-based home pregnancy tests in the very early weeks of pregnancy.
Many women worry about higher or lower than average hCG levels, but individual levels usually don't mean anything. Having a trend toward higher hCG levels can be normal or can be a sign of complications like molar pregnancy.