hCG test: normal levels and what the result means

Human chorionic gonadotropin (hCG) is a hormone produced by the placenta shortly after a fertilised egg implants in the uterus. The amount of hCG in the blood rises rapidly during the first weeks of pregnancy and is what both home and laboratory pregnancy tests are based on. According to MedlinePlus, in pregnant women hCG can be detected as early as 10 days after conception. There are two types of hCG test: qualitative (the answer is positive or negative) and quantitative (an exact concentration in mIU/ml), which makes it possible to follow how the amount of the hormone changes over time. In a healthy pregnancy hCG usually rises rapidly over the first weeks, and whether that pattern matches expectations is something a doctor assesses with a repeat test. Apart from pregnancy, hCG can also be used for other purposes — for example to detect a sign of certain ovarian or testicular tumours, because these tumours can also produce this hormone. In non-pregnant women and in men the amount of hCG in the blood is normally very low or absent.

• When pregnancy is suspected — a quantitative or qualitative blood test establishes whether a woman has conceived
• To follow the course of an early pregnancy and to assess whether the hCG level is rising as expected
• When an ectopic pregnancy, a threatened miscarriage or a pregnancy that is not developing is suspected
• To assess whether a miscarriage is complete — whether the hCG level is falling as it should
• In women with certain ovarian tumours or men with testicular tumours, where hCG is used as an additional marker
• To establish the approximate age of the pregnancy and in screening tests for pregnancy abnormalities (for example Down syndrome)

During pregnancy, an unexpectedly high hCG level compared with the gestational age can indicate a multiple pregnancy — twins or triplets, where each placenta produces its own amount of the hormone, so the total concentration in the blood is higher than would be expected for a single fetus. Outside pregnancy, a raised hCG is associated with certain tumours — choriocarcinoma, a hydatidiform mole, ovarian tumours in women or testicular tumours in men — because these tissues can also produce this hormone. The value is always assessed together with the gestational age or other tests, because a single isolated number without context tells little. According to MedlinePlus, the cause is usually clarified with an ultrasound scan and a repeat hCG measurement a few days later, in order to assess how the hormone is changing over time.

• A multiple pregnancy (twins, triplets)
• A hydatidiform mole — abnormal growth of pregnancy tissue in the uterus
• Choriocarcinoma — a rare tumour of placental tissue
• Ovarian tumours in women
• Testicular tumours in men

What usually follows a raised result

• An ultrasound scan to check the course of the pregnancy and the number of fetuses
• A repeat hCG test a few days later, so that the trend can be seen
• A consultation with a gynaecologist or an oncologist, if hCG is raised without a pregnancy
• Other tests assessed alongside it, depending on the suspected cause

A lower than expected hCG

During pregnancy, an hCG level lower than expected, or a failure to rise as it should, can indicate complications — an ectopic pregnancy, where the fertilised egg implants outside the uterus, a threatened miscarriage, or a fetal death in the uterus that has already occurred. It can also indicate an incomplete miscarriage, where part of the pregnancy tissue remains in the uterus. In a healthy early pregnancy hCG usually rises rapidly, so a rise that is too slow, or a fall, is regarded as a warning sign. Any mismatch between the hCG trend and the gestational age is assessed by a doctor together with an ultrasound scan, and not on the basis of one isolated value. According to MedlinePlus, a repeat hCG test after 48 hours is often ordered to check whether the amount of the hormone is changing as would be expected in a healthy pregnancy.

• An ectopic pregnancy — the fertilised egg has implanted outside the uterus
• A threatened miscarriage, or a miscarriage that has already happened
• An incomplete miscarriage, where part of the tissue remains in the uterus
• Fetal death in the uterus

• An ultrasound scan to confirm or rule out an ectopic pregnancy
• A repeat hCG test after 48 hours to assess the trend
• An urgent consultation with a gynaecologist, if an ectopic pregnancy is suspected
• Watching the symptoms — bleeding, pain — and discussing them with a doctor

Non-pregnant women, men and pregnancy: reading the right range

According to MedlinePlus, the normal hCG level in non-pregnant women is below 5 mIU/ml, and in men below 2 mIU/ml; during pregnancy the ranges are far wider and change every week — at week 5, for example, roughly 217–8,245 mIU/ml. The source gives no physiological explanation of why the limits for women and men differ — it only states separate normal limits for each group. Important: these figures are indicative, because different laboratories may use slightly different ranges and units. When a result is assessed, it has to be compared with the range for the person's own group (a non-pregnant woman), and not with the figures for men or those that apply during pregnancy, because the purpose and interpretation of hCG depend on whether the person is pregnant.

According to MedlinePlus, the normal hCG level in men is below 2 mIU/ml — a lower limit than for non-pregnant women, whose normal level is below 5 mIU/ml. During pregnancy — at week 10, for example — hCG can reach roughly 44,186–170,409 mIU/ml, which shows that in men this marker should in principle be almost zero, because hCG is usually produced by the placenta. The source does not explain why the limits for men and women differ (2 compared with 5 mIU/ml) — it only gives separate laboratory ranges for each group. When a test result for a man is assessed, it is important to use the limit intended for men, and not the ranges for women or for pregnancy, because different groups have different reference points depending on the laboratory's method.

According to MedlinePlus, the hCG reference ranges during pregnancy are far wider and change with the week of pregnancy — at week 3, for example, 5–72 mIU/ml, at week 6, 152–32,177 mIU/ml, and at week 10, 44,186–170,409 mIU/ml. That is considerably above the ranges for non-pregnant women (below 5 mIU/ml) and men (below 2 mIU/ml). The source states that these ranges are indicative and can differ depending on the laboratory, but it gives no physiological explanation of why the particular numbers are so large and vary so widely between weeks. When a result during pregnancy is assessed, what matters most is comparing it with the range for that specific gestational week and following the trend over time, rather than with a one-off level for a non-pregnant woman or a man.

Repeat tests and related pages

Because what matters in early pregnancy is the trend rather than a single figure, a doctor often repeats the quantitative hCG test after 48 hours or a few days and assesses it together with an ultrasound scan. Related pages: beta-hCG, oestradiol, progesterone, LH, prolactin, and tests during pregnancy in Lithuania.