What to know about HCG pregnancy tests

Typically, HCG levels increase steadily during the first trimester, peak, then decline in the second and third trimesters as the pregnancy progresses.
Doctors may order several HCG blood tests over several days to monitor how a person’s HCG levels change. This HCG trend can help doctors determine how a pregnancy is developing
Key points to know about HCG pregnancy tests include the following:
Home pregnancy tests are about 99% accurateTrusted Source when a person takes them correctly.
For the most accurate results, a person should not take an HCG test until after the first missed period.
A home test cannot detect pregnancy complications.
This article looks at HCG levels and how they relate to pregnancy. We also examine the potential results and accuracy of an HCG pregnancy test.
HCG pregnancy test overview
Many people have very low levels of HCG in their blood and urine when they are not pregnant. HCG tests detect elevated levels.
Some tests may not detect pregnancy until HCG has risen to a certain level. Tests that can detect lower levels of HCG may diagnose pregnancy earlier.
Blood tests are typically more sensitive than urine tests. However, many home urine tests are highly sensitive. A 2014 analysisTrusted Source found that four types of home pregnancy tests could detect HCG levels up to 4 days before the expected period, or about 10 days after ovulation for many people.

What is HCG?
Cells that become the placenta produce the hormone HCG. A person’s HCG levels quickly rise during the first few weeksTrusted Source of pregnancy.
HCG levels not only signal pregnancy but are also a way to measure whether a pregnancy is developing correctly.
Very low HCG levels may point to a problem with the pregnancy, be a sign of an ectopic pregnancy, or warn that pregnancy loss could occur. Rapidly rising HCG levels can signal a molar pregnancy, a condition that causes a uterine tumor to grow.
Doctors require multiple HCG measurements to track the development of a pregnancy.
HCG levels stop rising late in the first trimester. This leveling out may be why many people experience relief from pregnancy symptoms, such as nausea and fatigue, around this time.
Types of HCG tests
There are two types of HCG tests: qualitative and quantitative.
Qualitative HCG tests
A person can use this type of test to check for elevated HCG levels in the urine or blood. Urine tests are about as accurate as blood tests. A high level of HCG indicates that a person is pregnant.
A negative qualitative HCG test means a person is not pregnant. If they still suspect that they are pregnant, a person should repeat the test after a few daysTrusted Source.
False-positive results may occur if hormone levels are high due to menopause or hormone supplements. Some ovarian or testicular tumors may also raise a person’s HCG levels.
Learn more about false-positive pregnancy tests here.
Also called a beta HCG test, this blood test measures the specific HCG hormone in your blood in international units per liter (IU/L). The level of HCG helps determine the age of the fetus.
HCG levels rise in the first trimester and then slightly drop. They typically peak at 28,000–210,000 IU/L around 12 weeks after conception.
If HCG is higher than the average pregnancy level, it could indicate more than one fetus.

How to read the results
People must read the urine test instructions and follow them carefully. Most tests use lines to show when a test is positive. The test line does not have to be as dark as the control line to be positive. Any line at all indicates the test is positive.
An individual must check the test within the time frame the instructions indicate. This is typically around 2 minutesTrusted Source.
Test strips can change color as they dry. Some people notice an evaporation line after several minutes. This is a very faint line that may look like a shadow.
Learn everything you need to know about pregnancy tests here.
Accuracy
Each pregnancy is different, but home pregnancy tests are close to 99% accurateTrusted Source if a person uses them as instructed. False-positive results are rarerTrusted Source than false-negative results.
Due to how long it takes for HCG levels to rise, a person can be pregnant and still get a negative test. A positive result usually appears after retesting a few days later.
However, because home pregnancy tests are increasingly sensitive, some can detect very early pregnancies with low HCG levels.