Progesterone Level Interpretation: 7.3 ng/mL
A progesterone level of 7.3 ng/mL most likely indicates the early luteal phase of the menstrual cycle, suggesting recent ovulation has occurred but the corpus luteum has not yet reached peak progesterone production. This level is too low to confirm pregnancy but too high for the follicular or ovulation phases.
Clinical Interpretation by Menstrual Cycle Phase
What This Level Rules Out
Not follicular phase: The level of 7.3 ng/mL far exceeds the follicular phase range of 0.1-0.9 ng/mL, definitively excluding this phase 1.
Not ovulation phase: While 7.3 ng/mL falls within the broad ovulation phase range of 0.1-12.0 ng/mL, progesterone begins rising only after ovulation occurs, making this more consistent with early luteal phase 1.
Not postmenopausal: The level is dramatically elevated compared to the postmenopausal range of 0.0-0.1 ng/mL 1.
What This Level Suggests
Early-to-mid luteal phase (most likely): The level of 7.3 ng/mL falls within the luteal phase range of 1.8-23.9 ng/mL, but is on the lower end of this spectrum 1. In normal pregnancies, median progesterone levels range from 57.5 nmol/L (approximately 18 ng/mL) to 80.8 nmol/L (approximately 25 ng/mL) from 5-13 weeks gestation 1.
Adequate for confirming ovulation: A progesterone level above 3-4 ng/mL generally confirms ovulation has occurred, and 7.3 ng/mL meets this threshold 2.
Pregnancy Considerations
Unlikely to represent viable early pregnancy: The level of 7.3 ng/mL is substantially below the first trimester range of 11.0-44.3 ng/mL 1. In women with threatened miscarriage who subsequently had spontaneous miscarriage, progesterone levels ranged from only 19.0-30.3 nmol/L (approximately 6-9.5 ng/mL), which overlaps with this patient's level 1.
May indicate threatened miscarriage if pregnancy suspected: In the threatened miscarriage cohort, median progesterone levels were uniformly lower by approximately 10 nmol/L (3 ng/mL) at every gestational week compared to normal pregnancies 1. A level of 7.3 ng/mL would be concerning for pregnancy viability if pregnancy is suspected clinically.
Clinical Action Based on Context
If Timing Ovulation or Assessing Luteal Function
Repeat measurement in 5-7 days: Peak luteal progesterone typically occurs 7-8 days after ovulation. If this represents early luteal phase, a repeat level should show significant increase to 15-25 ng/mL in a normal cycle 3, 1.
Consider luteal phase deficiency if repeat level remains low: Progesterone levels that fail to rise above 10 ng/mL in the mid-luteal phase are associated with reduced fertility outcomes 2.
If Pregnancy is Suspected
Obtain quantitative β-hCG immediately: This is the definitive test to confirm or exclude pregnancy 4. The progesterone level alone cannot reliably distinguish early luteal phase from very early or failing pregnancy.
If β-hCG confirms pregnancy and progesterone remains 7.3 ng/mL: This represents a concerning finding. Normal early pregnancy should show progesterone levels >11 ng/mL by the time β-hCG is detectable 1. Consider transvaginal ultrasound to assess viability and location.
Common Pitfalls to Avoid
Do not use progesterone alone to diagnose pregnancy: While low progesterone is associated with pregnancy complications, the level of 7.3 ng/mL overlaps between late luteal phase and very early/failing pregnancy. Always correlate with β-hCG and clinical context 4, 1.
Do not assume adequate luteal function from a single measurement: One progesterone level of 7.3 ng/mL does not confirm adequate luteal phase support. Peak mid-luteal levels (typically day 21 of a 28-day cycle) should be measured for proper assessment 2, 1.
Do not start progesterone supplementation based solely on this level without clear indication: Progesterone supplementation in pregnancy is indicated for specific high-risk scenarios (prior preterm birth, short cervix), not for isolated low progesterone levels in early pregnancy without other risk factors 4, 5, 6.