Can Drinking Too Much Water Cause Low hCG Levels?

The term hCG stands for human chorionic gonadotropin, a hormone that your body makes during pregnancy.

When you take an at-home pregnancy test by urinating on a test strip, that test determines whether your body is producing hCG. If you are, it tells you that you're pregnant. The test can't tell exactly how much hCG your body is making (it's not what scientists would call a "quantitative" test), but your body needs to be producing a certain minimum amount in order for the test to detect it.

Drinking water—or any fluids—can, in fact, affect the results of this kind of at-home pregnancy test when very early in the pregnancy. If your urine becomes diluted and takes on a pale yellow or clear color, its level of hCG becomes lower.

If the level of hCG becomes so low that it's no longer detectable by an at-home urine-based pregnancy test, that test strip may indicate that you're not pregnant when you actually are. This is known as a false negative. This possibility is why doctors recommend taking at-home pregnancy tests first thing in the morning, before you start chugging fluids, like coffee.

Your hCG level rises for several weeks, peaking between week eight and 11 of pregnancy. It then decreases and levels off for the rest of your pregnancy.

Therefore, experiencing the type of "false negative" mix-up mentioned above is likely to happen only very early on in your pregnancy (like during the first week). After that beginning stage, even if your urine is diluted, your hCG level should still be high enough to be detectable by an at-home urine-based pregnancy test.

If you take an at-home urine-based pregnancy test very soon after trying to conceive and the result is negative, try waiting a few days—or even another week or two—and then taking the test again (as soon as you wake up in the morning) to make sure that the reading was correct. Most at-home urine-based pregnancy test kits come with two strips for this very reason.

Another option is to ask your doctor for a blood test that will determine whether you're pregnant with more accuracy. The fact is, even if an at-home urine-based pregnancy test shows that you are pregnant, your doctor may still want to confirm those results with a type of blood test. It's called a quantitative hCG blood test, because it can measure exactly how much hCG is in your blood. In this case, the amount of water that you drink should not affect the results, because fluids don't change the makeup of your blood.