Hormones
hCG
Pregnancy hormone from the placenta; shows whether you are pregnant and how an early pregnancy is progressing.
Everything about this testWhat it measures
hCG (human chorionic gonadotropin) is made by the placenta of a pregnant woman. At the start of a normal pregnancy, the amount in the blood roughly doubles every two to three days. Around the tenth week after the last period the value is at its highest, and after that it slowly falls; a few weeks after giving birth, hCG can no longer be measured. Unlike a pregnancy test from the shop, this blood test gives a number, so repeat tests show whether the value is rising or falling.
- Pregnancy
- How an early pregnancy is progressing with bleeding or abdominal pain: an hCG that rises too slowly may fit a (threatened) miscarriage or a pregnancy outside the womb
- Remaining pregnancy tissue after a miscarriage, if the hCG does not fall
- Rarely: a molar pregnancy (a non-viable pregnancy in which the placental tissue overgrows) or a tumor that makes hCG
High
In a woman of reproductive age, a raised hCG almost always means a pregnancy. One value does not show whether the pregnancy is progressing well or is in the womb; that requires a repeat measurement after a few days and an ultrasound. After a miscarriage or birth, hCG remains measurable for a few more weeks, and hCG injections (during fertility treatment or as a drug alongside anabolic steroid use) also give a raised value. After menopause, a slightly raised value can occur without pregnancy, because the pituitary gland makes a little hCG. Rarely: a strongly or persistently raised value fits a molar pregnancy or, in a man or non-pregnant woman, a tumor of the testicle or ovary.
Low
An unmeasurable hCG usually means that you are not pregnant. Very early after conception, the value can still be too low to show a pregnancy; a repeat test after a few days then gives clarity. In an early pregnancy, a value that rises too slowly, stays the same or falls fits a (threatened) miscarriage or a pregnancy outside the womb. After a miscarriage, a falling hCG is in fact normal.
Preparation
- Do you take biotin (vitamin B8, often in hair and nail supplements)? Stop at least 2 days before the sample is taken, or 4 days for a high dose.
If your result is abnormal
With a positive result without symptoms, the usual first contact with the midwife follows. With bleeding or abdominal pain in an early pregnancy, the GP or gynecologist repeats the hCG after a few days and arranges an ultrasound. With a raised hCG in a man or a non-pregnant woman, the measurement is repeated first, and if the result is confirmed, a referral to a specialist follows.
Reliability
As a pregnancy test, hCG in blood is reliable, provided it is not measured too early after conception. One value says little about how an early pregnancy is progressing: according to the Dutch Society for Clinical Chemistry (NVKC), doctors look at the rise between measurements, and in practice always together with an ultrasound. In men and non-pregnant women, a slightly raised value often has no disease as its cause and is repeated first. Outside a (possible) pregnancy, the result says little in people without symptoms.
Limitations
- Timing: too early after conception, the value may still be below the detection limit.
- Measurement methods and reference values differ per laboratory; preferably compare successive measurements from the same laboratory.
- hCG injections during fertility treatment or anabolic steroid use give a temporarily raised value.
- After menopause, a slightly raised value can occur without pregnancy; rare interfering antibodies in the blood and biotin supplements can disturb the measurement.
How common is this
About 1 in 10 pregnancies ends in a miscarriage. Fewer than 1 in 100 pregnancies grow outside the womb. A molar pregnancy or a tumor that makes hCG is rare.
Who is this useful for
Useful for women who want to know whether they are pregnant, and in an early pregnancy with bleeding or abdominal pain to follow its progress together with the midwife or GP. Also useful after a miscarriage to see whether the hCG is falling. With severe abdominal pain, dizziness or heavy bleeding in a (possible) pregnancy, a blood test is not the right first step: then direct contact with the GP, midwife or out-of-hours GP service is needed. Not useful for men or non-pregnant women without symptoms.
Downsides and risks
- A slightly raised value in a man or non-pregnant woman, for example after menopause or due to interfering antibodies, can lead to unnecessary worry and follow-up testing.
- One value in an early pregnancy can give false reassurance or cause worry; only the course over time and an ultrasound show how the pregnancy is developing.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results