Innovative technologies used during laboratory research provide accurate, reliable data. It is possible to determine the minimum concentration of a substance or compound.
Expert opinion
Kovaleva Elena Anatolyevna
Doctor-Laboratory Assistant. 14 years of experience in clinical diagnostic services.
Ask a question to an expert
A blood test for hCG is often used in diagnosis. Based on its results, it is determined whether a woman is pregnant or not , and whether a pathological process develops in this case.
What is hCG, its functions
Implantation of the fertilized egg - the beginning of hCG synthesis
Human chorionic gonadotropin (hCG) is a reproductive hormone that begins to be produced in large quantities after a fertilized egg is implanted into the uterine tissue. This process occurs at the very beginning of pregnancy - 5-6 days after the fusion of the egg with the sperm.
After implantation (penetration) into the endometrium of the uterus, which is the loose tissue lining the organ cavity, the fertilized egg begins to grow deeper into it, reaching the blood vessels. At this moment, in order to prevent mixing of the blood of the mother and the embryo (two genetically relatively foreign agents), the early precursor of the placenta, the syncytiotrophoblast, begins to form. This common organ of the “mother-embryo” system releases hCG into the blood in ever-increasing quantities.
From a chemical point of view, hCG is a complex protein structure, conventionally divided into two parts: alpha and beta. The alpha subunit makes hCG similar to some other active substances: thyroid-stimulating hormone (acts on thyroid cells, increasing its activity), progesterone (the so-called “pregnancy hormone”) and luteinizing hormone (sex hormone). The beta subunit is unique; its structure is unique to hCG, which makes it possible to carry out highly accurate detection of it in the blood.
Structure of hCG
The main function of hCG is to stimulate physiological changes in the body of a pregnant woman for normal gestation. Under the influence of hCG, the corpus luteum does not die off in the ovary of a pregnant woman after 14 days of the second part of the menstrual cycle, but continues to persist, releasing the necessary hormones into the blood.
Other functions of hCG are:
- Improving the nutrition of the placenta, maintaining its viability;
- Changes in the immune responses of a pregnant woman;
- Stimulation of ovulation in women and sperm production in men;
- Impact on specific cells of the male embryo, which leads to the correct formation of the male reproductive system.
Gonadotropin levels depending on the stage of pregnancy
An hCG test allows you to confirm the fact of conception and determine the timing of pregnancy. To obtain reliable data during diagnosis, the timing of the release of the egg from the ovary must be taken into account. For convenience, this period is denoted by the abbreviation DPO, that is, “day after ovulation.” Typically, such tests are carried out among women planning motherhood.
You might be interested in: Labor does not begin at 42 weeks of pregnancy: what to do?
In the initial stages, the growth of human chorionic gonadotropin does not occur at such a rapid pace as, for example, at 6-7 weeks. In this case, the results of the study may look something like this: “12 DPO – 20 mIU/ml.” All laboratories use an individual results table, which records data on the minimum, average and maximum hCG levels at a given time. The countdown starts from day 7 until day 42 of DPO.
If we take the average values, then at 7-8 DPO the minimum value will be no more than 2 mIU/ml, the average will be up to 5 mIU/ml, and the maximum will be up to 10 mIU/ml. In comparison, 42 DPO has a minimum of 28,000 mIU/ml, an average of 65,000 mIU/ml, and a maximum of 128,000 mIU/ml.
There are also certain tables that are used to compare results during pregnancies that have already taken place. Here, the beginning is taken from the moment of implantation of the embryo into the wall of the uterus (implantation of the fertilized egg or DPP) until 42 weeks. The table contains days of pregnancy and human chorionic gonadotropin concentrations.
It is important to note that in vitro fertilization (IVF) uses different tables. The days and indicators for embryos implanted 3 and 5 days after fertilization of the egg will be indicated here. Read more about hCG by week in this article.
Let us remind you that the interpretation of the results depends on the laboratory in which the woman was tested, and interpretation is performed exclusively by a specialist.
Normal hCG values
HCG levels vary by week
Normal hCG values depend on the analysis technique in a particular laboratory; when interpreting the results, you must rely on the numbers indicated on the form.
Most often, normal hCG values for men and non-pregnant women range from 0 to 5.0 mU/ml. Women after an abortion or childbirth are characterized by increased values that reach the specified norm within a week.
For pregnant women, there are precisely calculated norms for each week of fetal formation:
- 1st week - 20.0-150.0 mU/ml;
- 2 - 25.0-305.0 mU/ml;
- 3 - 1500.0-5000.0 mU/ml;
- 4 - 10000.0-30000.0 mU/ml;
- 5 - 20000.0-100000.0 mU/ml;
- 6-11 weeks - 20000.0-226000.0 mU/ml;
- 12 - 19000.0-130000.0 mU/ml;
- 13 - 18000.0-111000.0 mU/ml;
- 14 - 14000.0-80000.0 mU/ml;
- 15 - 12000.0-685000.0 mU/ml;
- 16 - 10000.0-585000.0 mU/ml;
- 17-18 weeks 8000.0-565000.0 mU/ml;
- 19 - 7000.0-50000.0 mU/ml;
- 20-28 - 1600.0-49500.0 mU/ml.
Causes of hCG deviations from the norm
HCG levels increase during pregnancy
The main reason for the increase in hCG in women of childbearing age is the onset of pregnancy. Most methods for self-express diagnosis of pregnancy are based on the determination of hCG - the so-called “test strips” of various modifications.
For those women in whom the possibility of pregnancy is excluded, as well as for men, elevated hCG is a formidable sign, since this hormone produces a large number of tumors:
- Cancer of the rectum and/or colon;
- Tumors from cells of the amniotic bladder or placental system (hydatidiform mole);
- Lungs' cancer;
- Tumors of the uterus;
- Malignant neoplasms in the kidneys;
- Oncological diseases of the testicles (testicles).
In pregnant women, reduced hCG is observed when:
- Frozen pregnancy;
- Fetal death;
- Threat of spontaneous abortion;
- Ectopic pregnancy;
- Placental insufficiency;
- The beginning of placental abruption;
- Severe pathologies of embryo development.
The doctor can correctly interpret the test result
However, it is worth remembering: there is always the possibility that the gestational age was set incorrectly for one reason or another; in this case, throughout the entire pregnancy, a slightly increased or decreased hCG may be observed (depending on whether a week more or less was “attributed” in the calculations ). For this reason, deviations of about 40-50% from the norm are often considered threatening.
Increased hCG values in pregnant women are observed when:
- Multiple pregnancy (and the more children there are, the higher the hCG throughout the entire pregnancy);
- Postterm pregnancy (when labor does not start on time);
- Severe toxicosis and other complications of pregnancy;
- Endocrinological diseases in the expectant mother;
- Genetic diseases of the fetus (Down syndrome, Patau and others).
Indications for analysis
Pain in the lower abdomen is one of the possible indications for the test
The most common indication for the test is the need to diagnose early pregnancy. Women can conduct such a test themselves using urine test strips available in pharmacies.
In women of childbearing age, hCG testing may also be indicated for:
- Delayed menstrual bleeding for more than 5-6 days;
- Amenorrhea (lack of menstruation);
- Severe irregularity of the menstrual cycle;
- Condition after taking emergency contraception (to confirm its effectiveness);
- Condition after abortion operations;
- Pain in the pelvic area;
- Bloody discharge or heavy bleeding from the vagina not associated with menstruation.
Urology patients may undergo testing
For men, the test is most often performed if the following symptoms are present:
- Unreasonable increases in body temperature;
- Erection disorders;
- Changes in the appearance of the testicles (testicles): reduction or enlargement, appearance of spots on them, painful swellings, change in skin color;
- Changes in body hair type.
For pregnant women, the analysis is indicated to monitor the development of the fetus; most often, the analysis is prescribed in conjunction with other studies. It is most important to monitor hCG levels for pregnant women who have the following risk factors:
- Age over 35 years;
- History of miscarriages;
- Inability to get pregnant for a long time;
- Endocrine diseases (diabetes mellitus type 1 or 2, hypothyroidism);
- Severe toxicosis in the early stages.
Preparing for the study
Both blood and urine can be tested
To test urine, you need to collect the morning portion in a clean container; before analysis, you must refrain from drinking excessive liquids; you should not take a diuretic.
To test your blood, you need to come for a test after a 4-5 hour break in food; the easiest way to do this is in the morning on an empty stomach. There is no need to stop taking medications, but you should inform your doctor about them.
To diagnose pregnancy in the early stages, blood should be donated no earlier than 6-7 days of delay in the menstrual cycle; at earlier stages, a false negative result is likely. After receiving the result, it is recommended to repeat the analysis after 2-3 days for confirmation.
How to take a hormone test - on an empty stomach or not
With all types of hormonal studies, the results of the analysis are influenced by stress, increased temperature due to infection, changes in diet, compliance with the rules of preparation - for example, whether blood was donated on an empty stomach or not. Therefore, for reliable results, it is important to take into account the recommendations:
- The last meal is 8-10 hours before.
- Schedule a visit to the laboratory in the morning.
- The day before the diagnosis there should be no physical or emotional overload, or consumption of alcoholic beverages.
- Do not undergo examination during exacerbation of diseases or viral infections with fever.
- If a woman is prescribed medications to stimulate ovulation or infertility therapy, then she should consult a doctor to determine whether they can be administered before the test or whether they need to be discontinued.
- All physiotherapy, massage, ultrasound and x-rays can be completed only after donating blood.
- Immediately before diagnosis, it is important to be at rest for at least 20 minutes; smoking is prohibited an hour before.
If an examination is scheduled after an abortion, at least 24 hours must pass. If hCG was introduced to treat infertility, then the minimum period for its determination in the blood is 3-5 days. Gynecologists usually refer for analysis no earlier than 7 days after the end of therapy.
Types of hCG tests
There are two main types of analysis for hCG: using a rapid test, which examines urine, and the ELISA method, which examines blood. During ELISA (immunological method), it is possible to determine both total hCG and beta-hCG. This type of analysis involves searching for a specific part of the hormone molecules - the beta subunit, which distinguishes it from all other types of active compounds.
The search for beta-hCG is considered a more reliable way to determine oncological diseases and tumor processes; to diagnose pregnancy, determining total hCG is sufficient.
Will the analysis show pregnancy before the delay?
Many women are at a loss as to how long a blood test will show pregnancy. So, already on the ninth day after expected ovulation you can donate blood for hCG. A blood test for pregnancy is the most reliable and early method among all existing ones.
About a week after fertilization, an increased increase in the hormone in the blood begins, which makes it possible to assess its dynamics and draw conclusions whether the woman is pregnant or not. An indicator of more than 6 mIU/ml is considered an affirmative result, and with repeated analysis, the hCG will double, which will confirm the onset of pregnancy and its successful development.
Decoding test results
Patients' blood is subjected to ELISA testing
When performing an analysis using the ELISA method, the result is given in the form of “Negative” or “Positive in the concentration ... mU/ml”. A “Negative” result should be considered as the absence of hCG in the blood - this is a normal result for men and non-pregnant women. Positive results must be interpreted in accordance with the standards given in the result form, as well as depending on the physiological state of the person:
- Conditions after childbirth, abortion, miscarriages are characterized by an increase in hCG for up to 1 week;
- After emergency contraception, hCG should remain normal if it is effective; an increase indicates pregnancy;
- After operations to remove tumors, hCG should most often return to normal, the patient’s condition must be kept under the control of an oncologist;
- An increase in hCG during pregnancy is physiological, but the attending physician must monitor this indicator; independent interpretation is unacceptable;
- In the last trimester of pregnancy, hCG gradually decreases; the degree of decrease and its speed should also be assessed only by a doctor.
How to prepare
When taking the hCG hormone, preparation for the test plays an important role. For the results to be correct, it is important for a woman to follow the following rules:
- 2 days before the study you need to stop drinking alcohol, fried and fatty foods. You shouldn't overeat either. Therefore, if a feast is planned the day before, it is better to postpone the test.
- The physical and psycho-emotional state of a woman during a blood test must be stable. It is necessary to exclude stress, strong emotional arousal, and intense physical activity. The period during which rest must be observed is 1-2 days.
- You should not eat food for 4-6 hours before the test. Doctors recommend giving up not only food, but also any drinks. In this case, the results will be the most reliable.
- You should refrain from smoking for 1 hour before taking hCG for pregnancy.
Important information: Table of the norms of the hormones FSH and LH during menopause in women
If you do not prepare for donating blood, the test results may be incorrect.
Reliability of hCG analysis
The reliability of the test must be confirmed by other methods
When diagnosing oncological diseases, the determination of hCG is an auxiliary method; on the basis of only one analysis it is impossible to determine the presence of a tumor. However, determining elevated hCG values is a reliable marker for identifying those people who may have pathology.
No type of hCG determination, including the beta subunit, can guarantee the absence of a tumor, even with a negative result. To diagnose oncological diseases, a full range of laboratory and instrumental studies is required.
When diagnosing pregnancy in the early stages, the determination of hCG is one of the most reliable indicators, while the determination of hCG in the blood by a laboratory method is considered more reliable. Self-diagnosis using urine test strips does not always give the correct result. To diagnose pregnancy, it is recommended to combine an hCG test with an ultrasound; an examination by a gynecologist is also absolutely necessary.
When is it recommended to donate blood?
Approximately 10-14 days after conception, the hormone exceeds the norm and begins to double daily. At this point, you can already donate blood to confirm pregnancy. After the fetus attaches to the wall of the uterus, gonadotropin already reaches a concentration of 10 mIU/ml, which indicates the onset of pregnancy. However, pharmacy tests do not yet show the presence of pregnancy.
There are several features when taking an hCG test:
- you need to donate blood for hCG no earlier than the ninth day after expected ovulation;
- after an abortion, analysis is prescribed in the first five days to exclude body debris in the uterus;
- after pregnancy is detected, after some time a hCG test is re-administered to monitor dynamics;
It is worth remembering that elevated levels of the hormone may increase depending on individual characteristics or in the presence of diseases.
Advice for a woman during the procedure
The biological material is venous blood. You can take the test on an empty stomach or in the daytime after several hours of fasting. The morning reading will be the most reliable. Before the diagnosis, you need to calm down and sit for 20-30 minutes. If you are taking any medications, be sure to inform the laboratory assistant. Deviations from normal hCG levels can be affected by alcohol, coffee, and poor nutrition, which disrupt hormonal levels.
Where to get tested
The procedure is carried out in any clinic or laboratory. Private institutions offer more comfortable diagnostics. They can send biomaterial to different cities or countries for its study in more qualified laboratories, and the price will be significantly higher than in the same antenatal clinic or clinic.
