Beta hCG test explained (β-hCG)

Beta human chorionic gonadotropin (β-hCG) is a hormone produced by placental cells shortly after a fertilised egg implants in the uterus. It reaches the blood and the urine as early as about day 10 after fertilisation, which makes it the most sensitive marker of early pregnancy — both home pregnancy tests and the laboratory blood test rely on this. The blood test determines the exact concentration of the hormone (quantitative β-hCG), so it can be used not only to confirm a pregnancy but also to follow how it is developing: in a healthy early pregnancy the concentration usually rises rapidly every few days.

Besides monitoring a pregnancy, the test is used when an ectopic pregnancy, a molar (hydatidiform) pregnancy or a risk of miscarriage is suspected, and also as part of prenatal screening for the risk of Down syndrome. In rarer cases, a raised β-hCG in men or in non-pregnant women may be linked to certain tumours, which is why the test is also used in cancer diagnostics.

• When pregnancy is suspected, or to confirm it with a blood test when a home test is unclear or an exact concentration is needed
• To follow an early pregnancy when the risk of miscarriage is increased — repeating the test after a few days
• When an ectopic pregnancy or a molar (hydatidiform) pregnancy is suspected
• As part of prenatal screening for the risk of chromosomal disorders (for example Down syndrome)
• In men or in non-pregnant women — when certain tumours are suspected (for example of the testicles or the ovaries), where β-hCG is used as an additional marker

According to MedlinePlus, the normal β-hCG level for non-pregnant women is below 5 mIU/ml. This figure is given as a separate limit that applies when pregnancy is not suspected or has already been ruled out — because during pregnancy the same hormone can reach from 5 to more than 200,000 mIU/ml, and the healthy limit for men is lower still, below 2 mIU/ml. The source does not explain why the specific limit for non-pregnant women is set at 5 mIU/ml compared with 2 mIU/ml for men — it gives only the laboratory ranges themselves. A result therefore has to be compared with the range that matches the person's situation at the time of the test, and not with one general figure, because different groups have different upper limits and different reference points.

According to MedlinePlus, the normal β-hCG level for healthy men is below 2 mIU/ml — a lower limit than for non-pregnant women (below 5 mIU/ml) and incomparably lower than during pregnancy, when the value can reach from 5 to more than 200,000 mIU/ml. The source gives separate ranges for the different groups, but it does not explain why the limit for men is lower than the one for women — these are separate laboratory reference points, not a physiological reason that the source describes. A result should be compared only with this limit, and not with the figures for women or for pregnancy, which are several times or thousands of times higher.

According to MedlinePlus, during pregnancy (from week 3 to week 18) β-hCG can vary from 5 to more than 200,000 mIU/ml — a range several thousand times wider than the one for non-pregnant women (below 5 mIU/ml) or for men (below 2 mIU/ml). The source states that the exact range depends on the week of pregnancy, but it does not give a more detailed breakdown by week. When a result obtained during pregnancy is being interpreted, the most important thing is the exact week of pregnancy on the day of the test, because the same concentration can mean different things in different weeks; comparing the value with the ranges for non-pregnant women or for men is not meaningful in this case.

A raised beta hCG

A raised β-hCG most often means pregnancy, and during pregnancy its size depends on the week. An unusually high value can indicate a multiple pregnancy, a molar (hydatidiform) pregnancy or, in rarer cases, tumours — choriocarcinoma, ovarian or testicular tumours. It is assessed together with an ultrasound scan and the clinical picture.

• Pregnancy — a normal physiological rise in β-hCG that increases as the pregnancy progresses
• A multiple pregnancy (twins, triplets)
• A molar (hydatidiform) pregnancy
• Choriocarcinoma
• Ovarian or testicular tumours (in men or in non-pregnant women)

What to discuss with a doctor after a raised result

• An ultrasound scan to confirm the course and the location of the pregnancy
• A repeat β-hCG test after a few days — to assess whether the concentration is rising at an appropriate rate
• If the person is a non-pregnant woman or a man — further tests to rule out a possible tumour

During pregnancy a β-hCG that is lower than expected, or that is not rising sufficiently, can indicate a complication of the pregnancy — an ectopic pregnancy, a fetus that has died or a threatened miscarriage. In such cases the test is usually repeated after 48 hours together with an ultrasound scan.

• An ectopic pregnancy
• A fetus that has died (a failed pregnancy)
• An incomplete miscarriage
• A threatened spontaneous miscarriage

What to discuss with a doctor after a low result

• A repeat β-hCG test after 48 hours — to assess how the level is rising
• An ultrasound scan to check the location and the viability of the pregnancy
• Urgent consultation with a doctor if there is also abdominal pain or bleeding

Related tests

Related indicators: hCG, progesterone, estradiol, prolactin, FSH and LH. See also how to read blood test results and tests during pregnancy in Lithuania.