Blood markers

Standard UK NHS blood tests carry more nutritional information than they are typically read for. The five-cell white blood cell differential, mean corpuscular volume (MCV), and platelet count each have well-established nutritional and clinical interpretations that most patients are not walked through when results are reported as normal or abnormal. The 3 entries in this section cover what these markers actually indicate about iron, B12, folate, zinc, selenium, and other nutritional status, alongside the non-nutritional causes that need to be excluded before drawing nutritional conclusions.

A full blood count is one of the most informative and least-explained tests in UK general practice. The NHS routinely reports adult ranges (WBC 4-11 x10⁹/L, MCV 80-100 fL, platelets 150-400 x10⁹/L) and flags values outside them, but the clinical significance of patterns within those ranges, and the nutritional drivers behind common abnormalities, are rarely explained in routine appointments.

The patterns matter. A raised MCV above 100 fL has a recognised nutritional cause (B12 or folate deficiency) and a more common non-nutritional cause in UK adults (alcohol excess); knowing which is operating depends on the rest of the blood film and history. A low MCV below 80 fL is most often iron deficiency, with thalassaemia trait the principal differential. A raised platelet count above 400 is most commonly reactive, with iron deficiency the leading nutritional driver via TPO-mediated mechanism; persistent values above 600 without a reactive cause prompt British Society for Haematology workup for myeloproliferative neoplasm including JAK2 V617F testing. Lymphopenia can reflect severe zinc or selenium deficiency, chronic stress, or post-acute illness. Eosinophilia points to allergy, parasitic infection, or drug reaction.

These markers are frequently the first signal that something nutritional is going on, often before symptoms are clear. They can also be misleading: a normal MCV does not exclude iron deficiency in mixed deficiency states, because concurrent B12 or folate deficiency raises MCV and can mask the microcytosis iron deficiency would otherwise produce. A single raised platelet count without context is not in itself diagnostic. The entries in this section walk through what each marker actually indicates, what the NHS reference ranges are, and where the nutritional story ends and the non-nutritional differential begins.

This is a summary of published research, not personal health advice. Discuss any health or supplement decisions with a qualified healthcare professional, particularly during ongoing care, pregnancy, or with chronic conditions.