Standard blood tests are designed to identify disease. They use reference ranges calibrated to detect clear pathology: anaemia, hypothyroidism, diabetes, liver dysfunction. Within those ranges, results are reported as normal. But normal on a standard blood test does not necessarily mean optimal, and it does not mean that the symptoms you are experiencing do not have a biochemical cause.
Functional testing looks at a different question. Instead of asking whether disease is present, it asks how well the body’s systems are actually functioning, and where subclinical imbalances may be driving symptoms that standard testing will not reveal.
What Functional Testing Can Assess
Nutrient status. Functional nutrient testing goes beyond the handful of markers included in a standard panel. It can assess intracellular levels of vitamins and minerals, organic acid markers that reflect how efficiently cellular energy production is occurring, and fatty acid profiles that indicate the balance of inflammatory and anti-inflammatory compounds in the body.
Gut function. Comprehensive stool analysis assesses the composition of the gut microbiome, the presence of pathogenic organisms, markers of intestinal inflammation, digestive enzyme sufficiency and intestinal permeability. SIBO breath testing identifies bacterial overgrowth in the small intestine. These tests provide information that is entirely outside the scope of standard gastrointestinal investigation unless significant pathology is already suspected.
Hormonal health. The DUTCH test (Dried Urine Test for Comprehensive Hormones) provides a detailed picture of sex hormone levels and their metabolites, cortisol patterns across the day and night, and oestrogen metabolism pathways. This is significantly more informative than a single-point serum hormone level for understanding hormonal imbalance.
Thyroid function. A full thyroid panel including TSH, free T3, free T4 and thyroid antibodies provides a much more complete picture than TSH alone, which is the standard primary care screening test.
Food reactivity. IgG food sensitivity testing identifies delayed immune reactions to specific foods, which can contribute to inflammatory and digestive symptoms that are difficult to identify through elimination diets alone.
When Is Functional Testing Appropriate?
Functional testing is most valuable when symptoms are present but standard investigation has not identified a cause, when the clinical picture suggests a specific mechanism that warrants confirmation before building a protocol around it, or when a baseline assessment of nutritional status is needed to guide a targeted supplementation plan.
It is not always necessary. A detailed clinical and dietary history often provides enough information to build an effective initial protocol, with testing used to refine and confirm as needed rather than as a routine starting point.
Claire Ward uses functional testing selectively, recommending it when the additional information it provides is likely to meaningfully change or improve the intervention. She interprets results within the context of the full clinical picture, not as standalone data points.
If you are curious about whether functional testing would be useful in your case, book a consultation with Claire at Hever Health and she will give you an honest assessment.