Which blood values to test when?
The cycle day decides whether your lab result means anything. The free PDF guide covers timing, preparation and the right question for every marker.
- Cycle timing: FSH, LH and estradiol on cycle day 2–3, progesterone mid-luteal.
- 18 markers at a glance – from ferritin and fT3 to ApoB and lipoprotein(a).
- Preparation checklist: fasting, biotin, exercise, infections, estradiol gel and the draw arm.
- Three sentences for your doctor’s appointment.
How to time perimenopause blood tests
- Identify your cycle day Note the first day of your last period. Day 1 is the first day of real bleeding — it defines every other window.
- Measure FSH, LH and estradiol on day 2–3 Only in this window are FSH, LH and estradiol comparable. Outside it, values can hardly be placed between cycles.
- Measure progesterone mid-luteal About 5–7 days after ovulation, around day 21 in a 28-day cycle. Only there does progesterone show whether the luteal phase held.
- Draw cycle-independent markers in the morning Thyroid, ferritin, vitamin D, HbA1c, lipids and testosterone: fasting and early, testosterone ideally before 10 a.m.
- Check the preparation Pause biotin supplements beforehand, avoid intense exercise and acute infections, and never apply estradiol gel to the draw arm.
- Read results as a trajectory A single value is a snapshot. Several measurements on the same cycle day show direction — the basis for your doctor conversation.
PeriTrack Insights