In a woman in her mid‑40s to early‑50s who received a Depo‑Provera (medroxyprogesterone acetate) injection, how soon after the injection should follicle‑stimulating hormone (FSH) be measured to assess menopause?

FSH Testing After Depo-Provera for Menopause Assessment

Wait at least 3 months (90 days) after the last Depo-Provera injection to check FSH, and require two consecutive elevated FSH levels (>35 mIU/mL) measured 90 days apart to confirm menopause, particularly in women ≥50 years old.

Timing and Rationale

The pharmacokinetics of Depo-Provera (medroxyprogesterone acetate) directly impact FSH measurement accuracy:

• MPA remains detectable for 120-200 days after a single 150 mg injection, with an apparent half-life of approximately 50 days 1
• Peak suppression of FSH occurs during active treatment, with FSH decreasing by 42-47% and remaining suppressed for up to 3-6 weeks after short-term MPA use 2, 3
• Serum MPA concentrations plateau at ~1.0 ng/mL for approximately 3 months, then gradually decline 4

Recommended Testing Protocol

Minimum Waiting Period

• Do not check FSH until at least 90 days (3 months) after the last injection when MPA levels begin declining below 0.5 ng/mL 4
• Ideally, wait until MPA becomes undetectable (120-200 days post-injection) for most accurate results 1

Confirmation Strategy

Two consecutive elevated FSH measurements are mandatory because:

• 40.6% of women with one elevated FSH (>35 mIU/mL) will have normal FSH on subsequent testing 5
• Only 43.7% of women with at least one elevated FSH had persistently elevated levels on repeat testing 5
• Single measurements are unreliable due to fluctuating FSH levels during the perimenopausal transition 5

Age-Specific Considerations

• Prioritize testing in women ≥50 years old, as they have greater likelihood of true menopause 5
• In women 40-49 years, FSH can be detected during DMPA use but requires more cautious interpretation 6

Critical Pitfalls to Avoid

1. Do NOT discontinue Depo-Provera before FSH testing - FSH can be measured during ongoing use without interrupting contraception 5, 6

2. Do NOT rely on FSH alone for monitoring adequacy of hormone replacement - FSH is not a reliable marker for estrogen dose adequacy, as inhibin also regulates FSH secretion 7

3. Do NOT use a single elevated FSH to diagnose menopause - This leads to premature discontinuation of contraception in 40% of cases 5

4. Recognize that amenorrhea on Depo-Provera does NOT indicate menopause - Amenorrhea is an expected effect of the medication, not a menopausal indicator 4

Practical Algorithm

For women 45-55 years on Depo-Provera questioning menopausal status:

1. Wait minimum 90 days after last injection (preferably 120-200 days)
2. Draw first FSH level
3. If FSH >35 mIU/mL → Wait another 90 days and repeat FSH
4. If second FSH >35 mIU/mL → Likely postmenopausal; consider discontinuing contraception
5. If second FSH <35 mIU/mL → Continue contraception; retest in 6-12 months if desired

This approach balances the prolonged pharmacologic effects of Depo-Provera with the clinical need to accurately determine menopausal status while avoiding unintended pregnancy in perimenopausal women.