hCG levels by week: how the pregnancy blood test is actually read.
A blood hCG level below 5 IU/L is considered not pregnant, and most laboratories call 25 IU/L or above a positive result. Beyond that, "normal" is a very wide band for every week of pregnancy. Doctors read the trend, especially the change over 48 hours, far more than any single number.
What hCG is and when it appears
Human chorionic gonadotrophin, or hCG, is a hormone made by the cells that become the placenta. Production starts when the fertilised egg implants in the lining of the uterus, usually 6 to 10 days after ovulation. From that point hCG enters your bloodstream and, a little later, your urine.
Its job in early pregnancy is to signal the ovary to keep producing progesterone, which holds the uterine lining in place until the placenta takes over around the end of the first trimester. hCG rises steeply through the first 8 to 11 weeks, peaks, then falls to a lower plateau. That shape is why a level that is "high" at 6 weeks can be ordinary at 16 weeks.
Blood test vs urine test: how early, how accurate
Both tests look for the same hormone. The difference is sensitivity and precision. A home urine test tells you whether hCG is above a threshold, typically around 20 to 25 IU/L, and is most reliable from the day your period is due. A quantitative blood test measures the exact amount, can pick up levels as low as about 5 IU/L, and can therefore be positive a few days earlier, often from about 10 days after conception.
That earlier window is real but small. Testing before implantation is complete can return a negative result in a pregnancy that is confirmed a few days later. If a first blood test is negative and your period still has not arrived, a repeat settles the question. Neither test can tell you how far along you are; dating relies on your last period and, later, an ultrasound.
Typical hCG ranges by week
The table below shows the sort of ranges laboratories and pregnancy resources publish. Weeks are counted from the first day of your last menstrual period, so "4 weeks" is roughly the week your period was due. Notice how wide each band is and how much they overlap. That is not a flaw in the table; it is how hCG behaves.
| Weeks since last period | Typical hCG range (IU/L) | What it usually means |
|---|---|---|
| Not pregnant | Below 5 | Negative. Between 5 and 25 is indeterminate and usually repeated. |
| 3 weeks | 5 to 50 | Implantation has just happened. |
| 4 weeks | 5 to 425 | Period missed; urine tests usually turn positive. |
| 5 weeks | 18 to 7,300 | Rapid rise; levels often double every 2 to 3 days. |
| 6 weeks | 1,000 to 56,000 | A heartbeat is often visible on ultrasound. |
| 7 to 8 weeks | 7,600 to 229,000 | Approaching the peak; doubling slows down. |
| 9 to 12 weeks | 25,000 to 288,000 | Peak levels, then the start of the decline. |
| 13 to 16 weeks | 13,000 to 254,000 | Falling towards the second-trimester plateau. |
| 17 to 24 weeks | 4,000 to 165,000 | Plateau; hCG is rarely measured at this stage. |
| 25 to 40 weeks | 3,600 to 117,000 | Stable lower levels until birth. |
Ranges vary by laboratory; your report shows the range your lab uses. These figures are indicative only and are counted from the last menstrual period, not from conception. They are not an Australian laboratory reference interval: Australian laboratories generally report a non-pregnant cut-off rather than week-by-week bands.
Two women at the same stage can have levels that differ tenfold and both go on to have healthy pregnancies. Twins tend to produce higher levels, and a dating error of a few days shifts where you sit in the table. Very high levels, or levels that do not fall as expected after a miscarriage, are also checked because of a rare placental condition called molar pregnancy. This is why no doctor will tell you how many weeks pregnant you are from an hCG number alone.
Why a single number matters less than the change over 48 hours
Because the ranges are so wide, one result rarely answers the questions people are actually asking: is this pregnancy progressing, and is it in the right place? In the early weeks, the trend answers those. Two results about 48 hours apart show whether the level is rising, plateauing or falling.
In a typically progressing early pregnancy, hCG roughly doubles every 2 to 3 days up to about 6 weeks, then slows. Doctors commonly regard a rise of at least about 50 percent over 48 hours as reassuring in the earliest weeks, and the expected minimum falls to about 35 percent once levels are higher, so slower rises still occur in pregnancies that continue normally. A normal rise does not by itself rule out a pregnancy developing outside the uterus.
A level that is rising slowly, flat or falling prompts closer follow-up, usually with an ultrasound, because it can point to an early loss or a pregnancy developing outside the uterus. It does not confirm either on its own. A level rising well is encouraging but not a guarantee. The number is one input; the scan and how you feel are the others.
Do you need to fast?
No. hCG is not affected by food, drink or time of day, so you can have a pregnancy blood test whenever suits you. If it is being drawn alongside tests that do need fasting, such as glucose, the collection centre will tell you, but the hCG itself never does.
When a doctor repeats the test
Most women never need a second hCG level. Repeats are used when there is a specific question to answer, for example:
- a first result in the indeterminate zone, between about 5 and 25 IU/L
- bleeding or one-sided pain in early pregnancy
- a previous ectopic pregnancy or early loss
- a pregnancy after IVF, where clinics often track hCG in the first weeks
- an early ultrasound that could not yet see a pregnancy in the uterus
- following levels back down to zero after a miscarriage or ectopic pregnancy
If your doctor asks for a repeat, use the same laboratory both times. Different labs use slightly different methods, and switching can look like a change in your level when it is not.
Ordering the KnowLuna pregnancy blood test
The KnowLuna pregnancy blood test is a quantitative beta-hCG, the same test a GP orders, priced at $59. A KnowLuna doctor requests it at no extra charge, blood is collected at an accredited (NATA/RCPA) centre near you, or with a home kit or a nurse visit, and a plain-English report arrives in your account. A 20-minute doctor consult can be added for +$59.
One honest note. If you have pain or bleeding, a self-ordered blood test is not the right first step. Contact your GP, an early pregnancy assessment service or an emergency department, who can arrange the blood test and an ultrasound together.
Common questions
Will a blood test 100 percent confirm pregnancy?
Very nearly. A quantitative hCG blood test is the most sensitive pregnancy test available, and a clearly positive result (well above 25 IU/L) is reliable. The exceptions are testing too early, before implantation has raised the level, and rare medical situations that raise hCG without a pregnancy, which is why a doctor reads the result alongside your history.
Is 7 days too early for a blood pregnancy test?
Seven days after ovulation is usually too early, because implantation may not have happened yet and hCG takes a few days to rise after it does. About 10 days after conception is the earliest a blood test is likely to be positive, and by the day your period is due it is reliable. A negative result taken very early should be repeated.
Am I pregnant if my hCG is 5?
A level of 5 IU/L sits right at the threshold. Most laboratories call under 5 negative and 25 or above positive, with results in between described as indeterminate. A level of 5 could be a very early pregnancy or could be the small amount of hCG some non-pregnant women have. A repeat test in 48 hours shows which.
Do I need to fast for a pregnancy blood test?
No. hCG is not affected by eating or drinking, so you can have the test at any time of day without fasting. If your doctor has ordered other tests at the same time, such as glucose, those may need fasting, but the pregnancy test itself never does.
What is a normal hCG level at 4 weeks?
Anywhere from about 5 to over 400 IU/L, counted from your last period. That spread is normal, and where you sit in it says little about the pregnancy. If your doctor wants to know how the pregnancy is progressing, a second level 48 hours later is far more informative than the first number.
Sources and further reading
- Pathology Tests Explained (RCPA): beta hCG quantitation
- Barnhart KT et al. Symptomatic patients with an early viable intrauterine pregnancy: hCG curves redefined. Obstet Gynecol 2004
- Healthdirect: hCG levels
- Pregnancy, Birth and Baby: hCG levels
- Pregnancy, Birth and Baby: pregnancy tests
General information only, not medical advice. If your symptoms are severe or sudden, see a doctor promptly. This page does not replace a consultation with a doctor who knows your history; read our medical disclaimer.