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This page describes products and general use; it is not medical advice.
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hCG test strips are single-use, dipstick-format immunoassays that detect human chorionic gonadotropin (hCG) in urine. The result is qualitative: a control line shows the strip worked, and a second line in the test region means hCG was detected at or above the strip’s stated sensitivity. This guide is for clinic staff, buyers and students who need to read a strip result correctly, understand what the printed sensitivity means, and handle strips and specimens as the insert directs.
Who uses it: clinic and point-of-care staff (professional-use strips), people testing at home (home-use products), and laboratory or procurement staff who stock and document them. Related reading: point-of-care testing, CLIA-waived tests and in vitro diagnostics.
What hCG test strips are
hCG is a hormone produced by the placenta during pregnancy (FDA). A test strip is the dipstick form of a pregnancy test: you immerse the marked end in a urine specimen and read the lines that develop on the membrane. A manufacturer’s instructions for use (IFU) describe the product used as an example here, the One Step+ hCG Urine Strip Test insert distributed by Henry Schein, as a rapid chromatographic immunoassay for the qualitative detection of hCG in urine, labelled for professional in vitro diagnostic use and categorised as CLIA waived. Other brands differ, so the insert in your own box governs.
How the strip works
In the example insert, a mouse anti-beta hCG antibody is conjugated to colloidal gold, and a goat anti-alpha hCG antibody is coated on the membrane in the test region. The specimen moves up the strip by capillary action. If hCG is present it binds the gold-labelled antibody and is captured at the test line, producing a coloured line. A separate control line should always appear; it confirms that enough specimen moved through the strip and the technique was sound.
Types: professional use and home use
| Type | Typical use | Key difference (as stated by the source) |
|---|---|---|
| Professional-use strip (example: One Step+ hCG Urine Strip Test) | Clinical and point-of-care testing | Insert states “for professional in vitro diagnostic use only” and CLIA category Waived; the result is a presumptive finding that a physician confirms (Henry Schein insert). |
| Home-use pregnancy test strip | Testing at home by the consumer | FDA notes most strips produce a coloured line if pregnant, but this depends on the brand; accuracy depends on following the instructions and interpreting the result correctly (FDA). |
Specifications that matter
The values below are from one product’s insert and are not typical of every strip. Check the figures printed in the insert for the strip you hold.
| Specification | Value in the example insert |
|---|---|
| Sensitivity (cut-off) | 25 mIU/mL hCG, standardised to the WHO Third International Standard |
| Read time | 3-4 minutes; the insert says not to interpret results after the read time |
| Dip time | At least 5 seconds, arrows toward the urine, not past the MAX line; then lay flat on a non-absorbent surface |
| Cross-reactivity tested | No cross-reaction with LH at 300, FSH at 1,000 or TSH at 1,000 uIU/mL |
| Specimen | Clean, dry container; first morning urine preferred because hCG is most concentrated, though any time of day may be used |
| Specimen storage | 2-8 C for up to 48 hours |
| Strip storage | Sealed pouch at 2-30 C; do not freeze; keep in the pouch until use; do not use past expiry |
| Upper detection limit | Reliably detects intact hCG up to 500,000 mIU/mL |
“Sensitivity” here means the lowest hCG concentration the strip is designed to detect. A strip with a lower cut-off number can detect lower concentrations, but the insert, not the number alone, defines how the product should be used.
How to read pregnancy test strip results
Read the strip at the time the insert gives, not before and not after. For the example strip:
| What you see | Meaning per the insert | Action per the insert |
|---|---|---|
| Two distinct red lines (control C and test T) | Positive: hCG detected | A positive is presumptive; confirmation is by a physician. |
| One red line at C, none at T | Negative: no hCG detected at or above the sensitivity | A negative can be a false negative if hCG is below the cut-off. |
| No control line | Invalid | Cause is insufficient specimen volume or incorrect technique; repeat with a new strip. |
| Faint line appearing after the read time | Not a valid reading | The insert says a weak line could indicate a low hCG level. |
How to read pregnancy test strip results: what the line cannot tell you
Line intensity varies, but the insert states that “neither the quantitative value nor the rate of increase in hCG can be determined by this qualitative test.” A darker line does not measure how far along a pregnancy is.
Pregnancy test strip accuracy and false negatives
How accurate are hCG test strips? Accuracy depends on following the instructions and on timing (FDA). FDA states that 10 to 20 of every 100 pregnant women will not detect their pregnancy on the first day of the missed period, because the placenta may not yet have produced enough hCG, and that a negative result should be considered a tentative finding.
In its performance section, the example insert reports a 150-specimen multicentre comparison (78 positive, 72 negative) with 100% agreement with a comparator strip. That is agreement between two strips, not a clinical accuracy figure for all products.
hCG test strips sensitivity: other limits
- Dilute urine can miss hCG.
- The example strip does not detect free-beta hCG or beta core fragments.
- Conditions other than pregnancy, such as trophoblastic disease and some tumours, can raise hCG (insert).
For context, the insert reports hCG detectable in urine and serum as early as 7-10 days after conception, often above 100 mIU/mL by the first missed period, peaking at 100,000-200,000 mIU/mL around 10-12 weeks.
How to choose
Selection points stated by the insert and FDA: check that the product is labelled for your setting: professional-use strips carry professional-use and CLIA-waived labelling, while home use is a separate product category covered by FDA’s consumer guidance. Compare the sensitivity printed in each insert, the read time, and the storage conditions, because these differ by brand. Staff who run professional strips should also follow the insert’s control schedule: the example insert recommends a positive control (25 mIU/mL) and a negative control (0) for each new lot, new shipment, monthly, and for each new operator.
Safe use and handling basics
- Bring strip and specimen to room temperature (15-30 C) before testing.
- Keep strips in the sealed pouch until use and do not use them past the expiry date.
- If the urine shows a visible precipitate, the insert says to centrifuge, filter or let it settle before testing.
- Discard used strips and specimens in a biohazard container, as the insert directs.
Clinical staff may also see urine hCG listed among waived tests in point-of-care testing. An ovulation test is a different product: see what an ovulation test is. For supply lists that include pregnancy tests, see the pregnancy resource center supply checklist.
Common mistakes
- Reading the strip after the read time and treating a late faint line as positive.
- Dipping past the MAX line or not immersing for the stated time, which can invalidate the strip.
- Reading line darkness as a measure of hCG level.
- Using an expired or improperly stored strip.
FAQ
How do I read a pregnancy test strip?
Wait for the read time in the insert (3-4 minutes for the example strip). Two distinct lines, control and test, is positive; one line at the control position is negative; no control line is invalid and needs a new strip.
What do hCG test strip results mean if the line is faint?
A faint line within the read time is still a line. A faint line that appears only after the read time should not be interpreted.
What does hCG test strip sensitivity mean?
It is the lowest hCG concentration the strip is designed to detect. The example strip is rated at 25 mIU/mL.
Can a pregnancy test strip be wrong?
Yes. A false negative can occur when hCG is below the strip’s cut-off, for example in very early pregnancy or dilute urine (FDA; insert). Technique and interpretation also affect the result.
Are professional and home-use strips the same?
Not necessarily. The example insert is for professional use under CLIA waived category, while FDA’s home-use guidance addresses consumer products; follow the insert supplied with the specific product.
Sources
- U.S. Food and Drug Administration, “Pregnancy” (home use tests): fda.gov/medical-devices/home-use-tests/pregnancy, checked 2026-10-30.
- One Step+ hCG Urine Strip Test instructional insert (Henry Schein): manufacturer insert PDF, checked 2026-10-30. Values apply to this product only.
