Bedside Snapshot
- Normal (Adult)
- Urine: negative when not pregnant. Serum: below the lab's cut-off. In pregnancy hCG rises fast, so read it against dates and the 48-hour trend, not a fixed range
- Critical Values
- No universal critical value. NICE (UK): ≥5,000 IU/L, or significant pain, a mass 35 mm or more, or a visible heartbeat, means surgery first-line; 1,500 to under 5,000 IU/L means methotrexate or surgery. Symptoms outrank the number
- High Suggests
- Intrauterine pregnancy (ultrasound confirms)
- Ectopic pregnancy: pain, bleeding, adnexal mass
- Molar pregnancy: hCG inconsistent with dates
- Low Suggests
- Too early in pregnancy, or a false negative: urine point-of-care tests are less sensitive at low levels, and a very high hCG (hook effect) can read falsely low
- Act Now If
- Positive test with pain and tenderness, bleeding or instability: treat as possible ectopic. Unstable goes straight to the ED; stable refers immediately to the early pregnancy service (NICE NG126). Notify receiving team
- Watch Out For
- A negative urine test does not clear a symptomatic patient, and an hCG value does not locate the pregnancy. Treat unknown location as possible ectopic until ultrasound locates it
Reference & Critical Ranges
Lab-specific ranges: Every lab, kit and analyzer sets its own cut-off. Use the cut-off on your report or the kit label. The values below are typical.
Reference ranges
| Population | Conventional | SI | Notes |
|---|---|---|---|
| Adult, not pregnant (urine) | Negative | Negative | Point-of-care cut-off is set by the kit; check its labeling |
| Adult, not pregnant (serum) | Below lab cut-off (mIU/mL) | Below lab cut-off (IU/L) | Assay-specific; mIU/mL and IU/L have the same numeric value |
| Pregnancy (serum) | Rises fast in early pregnancy | Rises fast in early pregnancy | No single normal range; read against dates and the 48-hour trend |
| Children & adolescents | Pre-pubertal: positive result is not pregnancy | Pre-pubertal: positive result is not pregnancy | Post-menarchal adolescent: treat as possible pregnancy. No pediatric hCG reference interval in the sources used; see Special Populations |
Severity & critical values
| Level | Conventional | SI | What it means |
|---|---|---|---|
| Negative (follow-up) | <20 mIU/mL | <20 IU/L | NICE expectant-management pathway (1.14.3) uses this as negative; the NICE methotrexate pathway (1.15.4) gives no number |
| Gestational sac seen | 3,510 mIU/mL | 3,510 IU/L | Level at which a sac was seen in 99% of viable pregnancies in a 2013 cohort; a missing sac below it does not settle the location |
| Expectant limit | 1,000 mIU/mL | 1,000 IU/L | Stable, pain-free tubal pregnancy under 35 mm with no heartbeat may be managed expectantly at this level or lower (NICE NG126) |
| Methotrexate limit | 1,500 mIU/mL | 1,500 IU/L | Methotrexate is offered below this level; from 1,500 to under 5,000, methotrexate or surgery is a choice (NICE NG126) |
| Critical | ≥5,000 mIU/mL | ≥5,000 IU/L | NICE (UK): surgery is first-line for tubal pregnancy at this level (NG126 1.15.2) |
Critical values: There is no universal critical hCG. For suspected tubal pregnancy, NICE (UK) uses ≥5,000 IU/L as the surgery trigger. That trigger pairs with significant pain, a mass 35 mm or more, or a visible heartbeat. An unstable patient goes to the emergency department whatever the number. So does one with significant concern about pain or bleeding (NICE NG126 1.4.1).
These are NICE (UK) criteria for in-hospital decisions, and US protocols may differ. EMS and transport crews don't pick treatment by the hCG value.
Conversion: For hCG, mIU/mL and IU/L carry the same number. You don't need a conversion factor.
Serial hCG change at 48 hours
(hCG at 48 h − hCG at 0 h) ÷ hCG at 0 h × 100 = % change
Run both samples in the same lab, on the same assay. NICE sets the bar at a rise of more than 63% or a fall of more than 50%. Those are NICE (UK) criteria. US cohort data show lower minimum 2-day rises in viable pregnancies. US criteria are different, so follow local protocol.
Causes of Abnormal Results
A positive hCG means pregnancy or another source of hCG. The hCG value alone doesn't name the cause. Clinical findings and ultrasound do (NICE NG126).
Positive result
| Cause | Clue |
|---|---|
| Intrauterine pregnancy | Gestational sac with a yolk sac or embryo on ultrasound; hCG rises more than 63% at 48 hours (NICE NG126) |
| Tubal (ectopic) pregnancy | Pain, bleeding, and an adnexal mass that moves separately from the ovary (sliding sign) or an empty sac (tubal ring) |
| Pregnancy loss | hCG falls more than 50% at 48 hours: pregnancy unlikely to continue, not confirmed (NICE NG126) |
| Molar pregnancy | hCG inconsistent with gestational age; a case report described a vesicular mole with hCG results that did not match the dates |
| Pregnancy of unknown location | Positive test with no intrauterine or extrauterine pregnancy on transvaginal ultrasound |
| Gestational trophoblastic neoplasia | hCG that stays positive or plateaus after a molar or other pregnancy; GTN can follow any gestation and is tracked with serial hCG |
| Recent pregnancy loss or delivery | hCG can stay detectable after the event; NICE advises review of a positive urine test after 3 weeks to rule out retained, molar or ectopic pregnancy (NICE NG126 1.11.8) |
Negative result (false negative)
| Cause | Clue |
|---|---|
| Too early in pregnancy | hCG below the test's detection limit; in one evaluation of point-of-care tests, false negatives clustered around 4 weeks' gestation |
| Low-level urine test | Point-of-care urine tests detected 53% (OSOM) and 78% (QuickVue+) of specimens at 20–300 IU/L; they are insufficient for very early pregnancy |
| High-dose hook effect | Very high hCG saturates the antibodies and reads falsely low; the test is negative despite pregnancy symptoms |
| Hook-like effect (variant hCG) | Some assays miss hCG variants that are common later in pregnancy; dilution is the fix |
False positive vs true positive
A true positive hCG can happen with no viable intrauterine pregnancy. Molar pregnancy is one example. A positive test proves hCG is there. It doesn't prove the pregnancy is viable, and it doesn't show where the pregnancy is. Only ultrasound and serial hCG answer those questions.
A positive serum hCG that doesn't fit the clinical picture can be a false positive. Heterophile antibodies cause it, and some call it phantom hCG. Urine can be negative in this case. Ask the lab to compare serum with urine. Ask for serial dilution or an alternative assay, because blocking reagents can miss cases.
Negative test with symptoms: A negative urine test doesn't rule out pregnancy while symptoms persist. Dilute and retest, or send a serum hCG. Manage the patient by their symptoms.
Interpretation & Bedside Approach
Step-by-step approach
- Is it pregnancy? Confirm the result: urine point-of-care or serum laboratory. A negative urine test can miss early pregnancy. So can a hook effect.
- How sick is the patient? NICE lists tachycardia over 100/min, hypotension under 100/60 mmHg, shock or collapse as signs of ectopic pregnancy (NICE NG126 1.4.4). Refer an unstable patient, or one with significant concern about pain or bleeding, directly to the emergency department (NICE NG126 1.4.1).
- Where is the pregnancy? With a positive test and no visible intrauterine pregnancy, you have a pregnancy of unknown location. Treat it as possible ectopic until ultrasound finds it.
- Trend the hCG: repeat at 48 hours in the same laboratory and calculate the percentage change.
- Classify the trend: use the NICE thresholds in the table below and the ultrasound findings together.
- Escalate or dispose: apply the NICE (UK) tubal pathway thresholds (1,000, 1,500 and 5,000 IU/L) with symptoms and ultrasound, then route per local protocol.
Serial hCG patterns
| Pattern | Suggests |
|---|---|
| Rise more than 63% at 48 h | Likely intrauterine pregnancy, but ectopic is not excluded: arrange ultrasound (NICE NG126) |
| Fall more than 50% at 48 h | Pregnancy unlikely to continue, not confirmed: counsel, then urine test 14 days later (NICE NG126) |
| Fall under 50% or rise under 63% | Abnormal trend: clinical review in the early pregnancy service within 24 hours (NICE NG126) |
| Serum progesterone | Not used to diagnose viable intrauterine or ectopic pregnancy (NICE NG126) |
Those 63% and 50% thresholds are NICE (UK) criteria. US cohort data show lower minimum rises. Follow local protocol.
Ultrasound finds the location. Look for an adnexal mass that moves separately from the ovary, with an empty sac or a complex mass. That raises the odds of tubal pregnancy. An intrauterine sac with a double decidual sign points to an intrauterine pregnancy (NICE NG126).
The 2013 cohort had 651 pregnancies. A gestational sac showed up in 99% of viable ones at a serum hCG of 3,510 mIU/mL. Sacs were first seen at 390 mIU/mL. Treat the discriminatory level as a population estimate. It is not a diagnostic cut-off for one patient.
Management Priorities
Emergency: suspected ectopic pregnancy with shock or collapse
- Stabilize: airway, breathing and circulation, per protocol. Oxygen goes on as your protocol directs (see Oxygen).
- Treat hemorrhage: manage shock per protocol. This is E3 guidance: don't hold an unstable patient for an hCG result or an ultrasound.
- Route: straight to the emergency department for an unstable patient, or one with significant concern about pain or bleeding (NICE NG126 1.4.1).
- Hand off: pregnancy test type and time, last menstrual period (not reliable for dating), Rh type, bleeding and blood pressure trend, and any drugs given.
Medications
| Drug | Adult dose | Pediatric dose (max) | Onset / key notes |
|---|---|---|---|
| Rh(D) immune globulin (anti-D) | NICE (UK): at least 250 units (50 mcg) IM at 12+0 to 12+6 weeks, for Rh(D)-negative patients having medical or surgical management (NG126 1.18.2). US labeling: 300 mcg (1,500 units) IM; the RhoGAM label lists Rh-negative ectopic pregnancy and pregnancy loss at any gestation as indications. The two approaches differ |
Same as adult for a post-menarchal adolescent; not applicable pre-pubertal |
NICE does not offer anti-D before 11+6 weeks (1.18.1). Decision is made in hospital; see the Rho(D) Immune Globulin page |
| Methotrexate (off label for ectopic pregnancy, NICE) | Hospital-only, protocol-dependent regimen (off label for ectopic pregnancy, NICE); regimen not restated here. See the Ectopic Pregnancy condition page |
Protocol-dependent for a post-menarchal adolescent (no pediatric regimen in sources used); not applicable pre-pubertal |
Verify pregnancy status before starting (product label); check the label's warnings before any dose |
Teratogens: Pregnancy status comes first. Confirm it before any drug with pregnancy warnings, methotrexate included. A teratogen goes to an unknown-status patient only on medical direction.
Definitive care & disposition
- Surgery first-line: significant pain, a tubal mass of 35 mm or more, a visible heartbeat, hCG of 5,000 IU/L or more, or inability to return for follow-up after methotrexate (NICE NG126 1.15.2). Use laparoscopy whenever possible.
- Methotrexate: no significant pain, unruptured tubal mass under 35 mm with no visible heartbeat, hCG under 1,500 IU/L, no intrauterine pregnancy, and able to return (NICE NG126).
- Expectant management: stable and pain-free, mass under 35 mm, no heartbeat, hCG 1,000 IU/L or less. Consider it from above 1,000 to below 1,500 IU/L (NICE NG126).
Those are hospital criteria, set by NICE (UK). US protocols may differ. Crews in the field don't pick treatment from an hCG number.
Doses are typical references. Follow local protocols, medical direction and institutional policy.
Field & Transport Considerations
Point-of-care testing
- Urine point-of-care test: Qualitative only. A negative result doesn't clear a symptomatic patient. Sensitivity is limited at low hCG levels.
- Hook effect: A negative test with pregnancy symptoms may mean very high hCG. The fix is dilution and a repeat test.
- Record: Test type, time and result. A point-of-care result doesn't replace a lab serum hCG when the result matters.
Before and during interfacility transport
- Obtain: pregnancy test result and time, last menstrual period (not reliable for dating), Rh type if known, bleeding trend (pad count), and pain score.
- Re-check: heart rate, blood pressure and SpO₂ at the interval in your protocol. NICE lists tachycardia and hypotension as signs of ectopic pregnancy (NICE NG126 1.4.4). Unstable patients go straight to the emergency department (NICE NG126 1.4.1).
- Do not delay: This is E3 guidance, not a NICE statement. Don't hold an unstable patient for an hCG result or an ultrasound.
- Stable with pain and tenderness: refer immediately to the early pregnancy service or out-of-hours gynaecology per local protocol (NICE NG126).
Timing & Kinetics
| Parameter | Value | Clinical implication |
|---|---|---|
| Serial interval | 48 hours | Compare with the same laboratory; calculate the percentage change (NICE NG126) |
| Rise threshold | More than 63% at 48 h | Likely intrauterine; not confirmed, and ectopic is not excluded (NICE NG126). NICE (UK) figure; US minimum rises are lower |
| Fall threshold | More than 50% at 48 h | Pregnancy unlikely to continue; repeat urine test 14 days later (NICE NG126) |
| Expectant follow-up | Days 2, 4 and 7 | Fall of 15% or more: repeat weekly until under 20 IU/L. No fall: senior review (NICE NG126) |
| Methotrexate follow-up | Days 4 and 7, then weekly | Until negative; reassess if hCG plateaus or rises (NICE NG126) |
| Early point-of-care false negatives | Around 4 weeks' gestation | Mean gestational age of false-negative urine tests in one evaluation: repeat if suspicion persists |
Special Populations
| Population | What changes | Clinical implication |
|---|---|---|
| Children & adolescents | Pre-pubertal: a positive result is not pregnancy. Post-menarchal adolescents can be pregnant | A positive result in a pre-pubertal child or a male needs medical evaluation per protocol and does not follow the pregnancy pathway on this page. Treat a post-menarchal adolescent as possible pregnancy (NICE NG126 1.4.5). Handle consent and confidentiality per local policy |
| Pregnancy | Symptoms count more than hCG; a low hCG does not make an unstable patient safe | Refer unstable patients directly to the emergency department (NICE NG126) |
| Rh(D)-negative pregnancy | Anti-D window differs by gestation and by guideline | NICE: no anti-D up to 11+6 weeks (1.18.1); at least 250 units (50 mcg) at 12+0 to 12+6 (1.18.2). US: the RhoGAM label lists ectopic pregnancy and pregnancy loss at any gestation (300 mcg, 1,500 units). Settle the approach with the treating team and the Rho(D) page |
| Cardiac arrest in pregnancy | Pregnancy-specific steps apply | Pregnancy-specific resuscitation steps apply; follow your protocol |
| Older adults | No age-specific hCG interval in the sources used | A positive hCG without pregnancy needs evaluation per protocol (see Causes) |
Pregnancy physiology: Pregnancy changes vital signs and assessment. For the normal changes, see the Pregnancy Physiology Assessment page.
Interfering Factors & Pitfalls
| Factor | Effect | Why | Avoid / fix |
|---|---|---|---|
| High-dose hook effect | False negative ↓ | Very high hCG saturates the antibodies | Dilute the sample and retest; send serum hCG |
| Hook-like effect | False negative ↓ | Assay misses a hCG variant common later in pregnancy | Dilute and retest; know which assay the lab uses |
Assay & device
| Factor | Effect | Why | Avoid / fix |
|---|---|---|---|
| Point-of-care urine kit | False negative ↓ | Detected 53% to 78% of urine specimens at 20–300 IU/L | Do not use to exclude early pregnancy when symptoms persist |
| Heterophile antibodies (phantom hCG) | False positive ↑ | Antibodies in the sample bind the assay, so hCG reads positive without pregnancy or a tumor | Compare serum with urine; ask for serial dilution or an alternative assay, since blocking reagents can miss cases |
| Kit and analyzer differences | Results differ between assays | Different antibodies and variant recognition | Trend on the same laboratory and assay |
Common misinterpretations
- "A negative urine test excludes pregnancy": Wrong. False negatives are documented, especially early and at high hCG.
- "The hCG level shows where the pregnancy is": Not true. hCG does not determine location (NICE NG126).
- "A low hCG means safe": Symptoms and clinical state outrank the hCG value (NICE NG126).
- "A reassuring 48-hour rise rules out ectopic": Not quite. A rise above 63% is likely intrauterine, but ectopic is not excluded (NICE NG126).
Physiology & Test Basics
What it measures
Human chorionic gonadotropin (hCG) is a glycoprotein hormone. You can detect it in urine and serum. Serum beta-hCG gives a number, and that number tracks pregnancy over time in emergency and early pregnancy care. This page covers the pregnancy test and the serum trend. It does not cover hCG-related thyroid effects.
Physiology & regulation
- hCG rises fast in early pregnancy. One value means little without dates and a repeat.
- hCG comes in several variant forms. Assays differ in which ones they detect.
- A serum hCG that falls on a repeat sample suggests the pregnancy isn't continuing (NICE NG126).
How it is measured
- Urine: A point-of-care qualitative test. The kit sets the cut-off.
- Serum: Quantitative immunoassay, reported in mIU/mL (or IU/L). Keep the same lab for the trend.
- Specimen: The lab sets the tube type and turnaround. Ask the lab when it's urgent.
Why it matters
A positive hCG confirms pregnancy and starts the pregnancy pathway. In emergency care, three questions change the transport. Where is the pregnancy? Is the patient unstable? What is the Rh type? Symptoms, ultrasound and the trend decide the next step.
Clinical Pearls
Pregnancy of unknown location: Treat it as possible ectopic until you know where it is. Don't use hCG to find the location (NICE NG126).
Symptoms over the number: A low hCG doesn't make a symptomatic patient stable. Symptoms outweigh the hCG result (NICE NG126).
Hook effect: A negative urine test with pregnancy symptoms can be a hook effect. Dilute the sample and retest. Or send serum hCG.
Transport: A positive test with pain and tenderness means immediate referral. The patient can look well and still need it (NICE NG126).
Rh status: An Rh(D)-negative patient needs an anti-D decision on the pregnancy pathway. NICE and the US label differ on window and dose. See the Rho(D) Immune Globulin page (NICE NG126; RhoGAM label).
Monitoring: Check the trend at 48 hours. A rise under 63% or a fall under 50% gets clinical review within 24 hours (NICE NG126).
Result does not fit the picture: Ask the lab to compare serum and urine hCG. Ask it to check for heterophile interference or a hook effect with serial dilution.
Verify pregnancy first: The methotrexate label says to verify pregnancy status before starting. Use in non-neoplastic disease is contraindicated in pregnancy (DailyMed label, revised December 2025).
References
- National Institute for Health and Care Excellence. (2019; last updated 17 June 2026). Ectopic pregnancy and miscarriage: diagnosis and initial management (NG126). NICE guideline. https://www.nice.org.uk/guidance/ng126
- Connolly AM, Ryan DH, Stuebe AM, Wolfe HM. (2013). Reevaluation of discriminatory and threshold levels for serum β-hCG in early pregnancy. Obstetrics & Gynecology, 121(1), 65–70. https://doi.org/10.1097/AOG.0b013e318278f421
- Greene DN, Schmidt RL, Kamer SM, Grenache DG, Hoke C, Lorey TS. (2013). Limitations in qualitative point-of-care hCG tests for detecting early pregnancy. Clinica Chimica Acta, 415, 317–321. https://doi.org/10.1016/j.cca.2012.10.053
- Griffey RT, Trent CJ, Bavolek RA, Keeperman JB, Sampson C, Poirier RF. (2013). "Hook-like effect" causes false-negative point-of-care urine pregnancy testing in emergency patients. Journal of Emergency Medicine, 44(1), 155–160. https://doi.org/10.1016/j.jemermed.2011.05.032
- Accord Healthcare, Inc. (2025). Methotrexate injection [prescribing information], revised December 2025. DailyMed, U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=dd035a9f-cd40-4314-b9d8-2294b8a924e2
- Kedrion Biopharma Inc. (2025). RhoGAM Ultra-Filtered PLUS (human Rho(D) immune globulin) [prescribing information], revised June 2025. DailyMed, U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d87e4d0b-2442-4135-b3f9-5c4f74845b87
- Jara-Aguirre JC, Baumann NA, Block DR, Algeciras-Schimnich A. (2019). Human chorionic gonadotropin suspected heterophile interference investigations in immunoassays: a recommended approach. Clinical Chemistry and Laboratory Medicine, 57(8), 1192–1196. https://doi.org/10.1515/cclm-2018-1142
- Elias KM, Berkowitz RS, Horowitz NS. (2019). State-of-the-Art Workup and Initial Management of Newly Diagnosed Molar Pregnancy and Postmolar Gestational Trophoblastic Neoplasia. Journal of the National Comprehensive Cancer Network, 17(11), 1396–1401. https://doi.org/10.6004/jnccn.2019.7364
Medical Disclaimer
- For Educational Purposes Only: This content is intended for educational reference and should not be used for clinical decision-making.
- Not a Substitute for Professional Judgment: Always consult your local protocols, institutional guidelines, and supervising physicians.
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