Best Time to Check AMH
AMH can be measured at any time during the menstrual cycle, as serum levels remain stable throughout both follicular and luteal phases. 1
Timing Flexibility for AMH Testing
AMH does not require cycle-specific timing unlike FSH, which must be measured on cycle days 2-5 of the menstrual cycle. 2
Multiple prospective studies in normo-ovulatory women demonstrate no significant fluctuations in AMH levels when measured on different cycle days, whether expressed by cycle day or aligned according to ovulation day. 1
Serial measurements throughout the menstrual cycle show remarkably stable AMH concentrations, with the highest value at day -12 (3.9 ± 1.3 ng/ml) and lowest at day 14 (3.4 ± 1.1 ng/ml)—a difference that is not statistically significant. 3
Minor Fluctuations Are Not Clinically Relevant
While some studies detect a slight statistical decrease in AMH after ovulation, with follicular phase levels being marginally higher than luteal phase levels, these fluctuations are smaller than intercycle variability. 4, 5
The minor variations observed do not alter clinical utility or change the timing recommendations for AMH measurement in daily practice. 5
Strong positive correlations exist between follicular and luteal AMH levels across all ovarian response groups (hypo-response, normo-response, and hyper-response), with Spearman's r values ranging from 0.822 to 0.899. 4
Special Considerations for Amenorrheic Women
For women with amenorrhea, AMH should be measured randomly rather than waiting for a specific cycle day, as recommended by the American Society of Clinical Oncology. 2
This contrasts with FSH testing in amenorrheic women, which also should be measured randomly but serves a different diagnostic purpose. 2
Clinical Advantage Over Other Markers
AMH's cycle-independent stability makes it superior to FSH for ovarian reserve assessment, as FSH requires precise early follicular phase timing (days 2-5) and can be falsely reassuring if estradiol is elevated. 2
AMH represents the best endocrine marker for assessing age-related decline in ovarian reserve in healthy women, according to the American Society of Clinical Oncology. 2
Important Caveats
AMH has no established role in diagnosing premature ovarian insufficiency (POI), despite its utility in ovarian reserve assessment. 2
Age-specific reference ranges are vital, as AMH levels are high in adolescence and fall with age, particularly after menopause. 6
Significant technical issues exist regarding AMH assays, including lack of international standardization and variability in sample handling, which can affect result interpretation more than menstrual cycle timing. 6