Use this tool to interpret a progesterone test in early pregnancy. Enter your value, unit, and gestational age or days past ovulation to see a level band and next steps.
How this estimate works
- Context choice: users can interpret by gestational age (weeks+days) or DPO (days past ovulation). Both are approximations because ovulation and implantation timing vary (NICE NG126).
- Expected ranges: we use broad, lab-style ranges for early pregnancy that rise modestly across weeks; thresholds are framed to avoid false reassurance or alarm and to emphasise trend over single values (ACOG: Early Pregnancy Loss).
- Level bands: the measured value is classified as Below expected, Indeterminate/borderline, Within expected, or Above typical. Borderline results prompt retesting instead of firm conclusions (RCOG patient info).
- Pair with hCG: we surface a 48–72-hour retest window and recommend interpreting progesterone alongside serial hCG and ultrasound when indicated (ASRM guidance on early pregnancy labs).
Units and conversion
Inputs accept either unit. The converter uses 1 ng/mL = 3.18 nmol/L (standard SI factor used across clinical labs).
Supplementation effects
- Vaginal: supports the endometrium with relatively modest serum levels due to uterine first-pass; effective exposure may not equal serum peaks (Paulson et al., 1999).
- Oral: variable serum due to first-pass metabolism; numbers can appear lower (DailyMed: micronized progesterone).
- IM injection: produces high serum peaks; a sample drawn soon after a dose may read high without indicating excessive uterine exposure (DailyMed: progesterone injection).
- Timing: we ask “hours since last dose” to remind that near-dose blood draws can skew interpretation.
Symptoms and safety
Bleeding or significant pain should prompt clinical advice regardless of a single progesterone value. Early follow-up is recommended when symptoms change (NICE NG126).
Limitations
- Reference intervals vary by lab, assay, and population; using the same lab reduces variance.
- Progesterone alone cannot diagnose a healthy or non-viable pregnancy; use with hCG trend and ultrasound when appropriate (ACOG).
- Supplement route and timing alter serum levels without directly reflecting uterine exposure.
- Borderline values near lower cut-points are common and often need repeat testing rather than immediate conclusions.
- NICE NG126: Ectopic pregnancy and miscarriage — assessment and follow-up pathways; emphasis on trends and ultrasound confirmation.
- ACOG Practice Bulletin: Early Pregnancy Loss — evaluation with serial hCG and ultrasound; cautions interpreting single labs.
- ASRM guidance on early pregnancy laboratory testing — role of serial testing and timing.
- Paulson et al., Fertil Steril, 1999 — differences in serum/uterine exposure with vaginal vs IM progesterone.
- DailyMed drug labels — pharmacokinetic notes for micronized progesterone and injectable forms.
How to use this calculator
- Enter your progesterone result and choose the unit (ng/mL or nmol/L). The tool can convert units.
- Enter gestational age in weeks and days, or days past ovulation if you are tracking DPO.
- Tell the tool if you are on progesterone support and the form used (vaginal, oral, or IM) if shown.
- Optional: add symptoms such as bleeding or cramping to tailor the retest guidance.
- Read the level band for your GA/DPO, retest timing (usually 48–72 hours), and a reminder to interpret results with serial hCG.
Educational only, not medical advice. Exogenous progesterone can inflate serum levels. Seek care for heavy bleeding, severe pain, dizziness, or fainting.
Frequently asked questions
What does progesterone do in early pregnancy?
Progesterone supports the uterine lining and helps maintain early pregnancy. Levels vary by person and timing.
How do I convert ng/mL to nmol/L?
The calculator converts units for you. As a guide, 1 ng/mL is about 3.18 nmol/L.
Do supplements affect the result?
Yes. Vaginal, oral, or intramuscular progesterone can raise measured levels. Results include a caution if you are on support.
Should I repeat the test?
Single results can be hard to interpret. Many clinicians repeat progesterone and pair it with serial hCG after 48–72 hours.
Can a low level predict miscarriage?
Low levels can be associated with risk, but they are not diagnostic on their own. Interpretation is strongest with ultrasound and hCG trends.
When should I seek urgent care?
Seek urgent care for heavy bleeding, severe pain, shoulder pain, dizziness, or fainting.