What a standard blood panel actually measures
When a GP orders "routine bloods", the panel typically includes a full blood count, a basic metabolic panel, liver function tests, and perhaps a thyroid screen. These tests are valuable for identifying acute abnormalities and tracking certain conditions over time. They are not designed to give a comprehensive picture of nutritional status. They are not designed to identify the subtle but clinically significant deficiencies that accumulate in people with chronic inflammatory and autoimmune conditions and that directly impair the function of the systems those conditions affect.
The gap between what the standard panel measures and what nutritional status actually requires is not a secret. Most clinicians are aware that their standard toolset is limited in this domain. What is missing is the system — the clinical infrastructure and the time — to do more. A GP with a 10-minute appointment and a patient with three active conditions cannot easily add a comprehensive micronutrient panel to the consultation. And without the context of the full clinical picture, even the results would be difficult to interpret usefully.
"Nutritional deficiencies in the context of chronic illness are not a side issue. They are often mechanistically central to the condition — both as contributing causes and as barriers to recovery. Identifying them requires testing beyond what routine care provides."
The most clinically significant gaps
Vitamin D
Perhaps the most immunologically important micronutrient. Vitamin D receptors are present on virtually every immune cell. Deficiency is directly implicated in autoimmune disease susceptibility. A serum 25-OH-D below 75 nmol/L is now considered suboptimal in the context of autoimmune and inflammatory disease, yet many labs flag deficiency only below 50 nmol/L.
Magnesium
Involved in over 600 enzymatic reactions in the body, including ATP production, DNA repair, and inflammatory regulation. Serum magnesium is a poor marker of cellular magnesium status — red blood cell (RBC) magnesium or magnesium loading tests are far more meaningful.
Omega-3 index
The ratio of EPA and DHA to total fatty acids in red blood cell membranes is one of the most clinically informative cardiovascular and inflammatory markers available. It is rarely ordered in standard care despite robust evidence for its relevance in autoimmune and inflammatory disease.
B-vitamin complex
B12, folate, B6, and B2 are essential cofactors in methylation, which governs gene expression, neurotransmitter synthesis, and immune regulation. Serum B12 within the 'normal' range can mask functional B12 deficiency — methylmalonic acid and homocysteine provide a more accurate picture.
Zinc and copper
Zinc is essential for immune cell development, thyroid function, and gut barrier integrity. Copper levels should be assessed in proportion to zinc, as the copper-zinc ratio matters more than either value alone. Both are commonly depleted in inflammatory conditions.
Iron studies
Beyond a standard haemoglobin check, a complete iron panel includes serum iron, transferrin saturation, ferritin (as both an iron marker and an inflammatory marker), and TIBC. Functional iron deficiency — where stores are present but iron is not available for use due to inflammation — requires this extended picture.
Why reference ranges mislead
Most nutritional reference ranges are calculated from population statistics — they define the range within which the middle 95 percent of the tested population falls. This is a statistical construct, not a clinical optimum. A level of vitamin D that places you in the 10th percentile of the population is not the same as a level that supports optimal immune function. A B12 level that is "within the normal range" may still be insufficient for a person with a specific methylation polymorphism or an inflammatory condition that increases demand.
In functional and integrative medicine, reference ranges are often interpreted differently — with target ranges that reflect not population distribution but the values associated with optimal physiological function in the relevant literature. This distinction matters enormously when results come back "normal" and symptoms persist. Normal is not the same as optimal. And optimal is what people with chronic conditions need to aim for.
Interpretation in context
A nutritional result means little outside its clinical context. A ferritin of 40 µg/L is in the standard reference range, but in someone with chronic fatigue and inflammatory disease, may represent a functional deficiency. This interpretation requires knowing the whole picture.
Building the nutritional picture into coordinated care
Comprehensive nutritional assessment is most useful when it is integrated with the rest of a patient's clinical data — their inflammatory markers, their symptoms, their medication list, their dietary history. A nutritional therapist who has access to the patient's full clinical picture can make recommendations that are genuinely personalised. A supplement protocol that does not account for drug interactions, known genetic polymorphisms, or the patient's specific inflammatory pathway is, at best, generic. At worst, it creates new problems. Integration is what makes nutritional medicine clinically excellent rather than merely well-intentioned.