Iron deficiency (low ferritin, with or without anaemia): confirm and look for the cause

Laboratory tests

• FBC (if not already done with the ferritin)if neededThe search for iron deficiency starts with the full blood count ^[1,2]: haemoglobin level and MCV are part of the estimate of gastrointestinal cancer risk ^[3].
• IgA anti-tissue transglutaminase antibodies (tTG-IgA) (coeliac disease)
• Total IgA (if coeliac disease suspected despite negative antibodies)if needednon-French guidelineIgA deficiency makes IgA-class antibodies falsely negative; it explains only a minority of seronegative coeliac disease and routine measurement has a low yield ^[3].

Urine tests

• Urine dipstick (microscopic haematuria)

Laboratory tests

• FBC (if not already done with the ferritin)if neededA full blood count is needed to distinguish iron deficiency without anaemia from iron-deficiency anaemia ^[1,2].
• IgA anti-tissue transglutaminase antibodies (tTG-IgA) (if digestive signs, recurrent or unexplained deficiency)if neededNo explicit recommendation for iron deficiency without anaemia: routine coeliac disease screening is recommended only in iron-deficiency anaemia ^[3]. To be discussed depending on the context; the French laboratory fee schedule (NABM) covers this test when coeliac disease is suspected ^[5].

Fasting laboratory tests, in the morning

• CRP
• Serum iron and transferrin with transferrin saturation (in the morning, fasting)
• FBC (if not already done)if neededThe work-up starts with the full blood count ^[1,2].
• Serum creatinine with eGFR (if renal function unknown)if neededChronic kidney disease is one of the situations in which ferritin may be normal despite insufficient iron stores ^[1,2].

2 to 4 weeks after starting iron

• FBC (response to iron)

After normalisation: every 3 months for 1 year, then every 6 months for 2 to 3 years

• FBC
• Serum ferritin (depending on the cause, to check that stores have been replenished)if needednon-French guidelineRecommended by the German DGHO (Onkopedia, 2025): after haemoglobin has normalised, FBC and ferritin every 3 months for about one year depending on the cause, with a ferritin target of 50 µg/L ^[6]. The British BSG, which this tab follows, considers the data insufficient for routine ferritin monitoring ^[3]. Option to check that stores have been replenished, for example after intravenous iron, at least 4 weeks after the infusion ^[6].