Reading a lab report critically

Three things worth understanding about how fertility labs get interpreted:

1. Timing changes the answer. “Day 21 progesterone” assumes a 28-day cycle with ovulation on day 14. If you ovulate on day 18, day 21 is only 3 days post-ovulation — progesterone hasn’t peaked yet. This is why Filia times a progesterone draw from the Peak day you log in Cycle tracking (Peak +7, for example) rather than a fixed cycle day.

2. Reference ranges are population-based and wide. A laboratory’s range covers the middle 95% of the people it tested, so a result inside the range can still be worth discussing — ferritin of 15 is reported as normal, but iron-deficiency symptoms are common below ~50. The reverse is also true: many narrower “fertility-optimal” targets circulating online are not backed by outcome data, and a result outside one of them is not a diagnosis. Your laboratory’s range plus your history and symptoms is what your clinician interprets.

3. The form of the test matters. Serum magnesium measures only about 1% of body stores, so RBC magnesium tracks status more closely. Total testosterone without SHBG can be misleading, because SHBG determines how much is biologically available.

Your results in Filia show the laboratory’s own reference range. Filia does not swap in a narrower research range, and nothing here is a diagnostic cutoff or a substitute for clinician interpretation.