Iron deficiency by serum ferritin (WHO 2020)
who2020_iron_deficiency_ferritin@1.0Table 1, iron deficiency, serum ferritin (µg/L): Children under 5 years <12 (apparently healthy), <30 (infection or inflammation); Adults (20–59 years) <15, <70; Pregnant women <15 (first trimester)
World Health Organization, WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations (2020) · Executive summary, recommendations 1.1-1.2 (PDF page 11) and Table 1 (PDF page 12) · source
Contested: Ferritin cut-offs for iron deficiency vary widely between bodies and studies (the guideline's own review cites thresholds from <12 to <30 µg/L in pregnancy); WHO's are low (high specificity). Other bodies (e.g. gastroenterology guidance) use higher values; those texts were not opened.
Not encoded: Pregnancy after the first trimester, and pregnancy with infection or inflammation: Table 1 gives no cut-off ('—'), so not assessable. Iron overload thresholds (Table 1 right half) are not encoded. Whether inflammation is present is supplied by the caller; CRP/AGP thresholds and population correction factors (question 4) are not applied.