A detailed breakdown of what the NHS includes and excludes in standard blood testing, which critical markers are routinely missed, and how comprehensive private testing fills the gaps.
A standard NHS GP blood test checks 5-15 biomarkers: typically a full blood count, basic kidney function, liver function, and sometimes TSH and fasting glucose. It does not check ferritin, Free T3, vitamin D, fasting insulin, HOMA-IR, hormones (testosterone, oestradiol, progesterone, cortisol, DHEA-S), advanced lipids (ApoB, lipoprotein(a)), cancer markers, immunoglobulins, coeliac screening, or urinalysis. A private comprehensive blood test checks all of these. The TrueVitals Ultimate panel tests 110 biomarkers for £349 with a 60-page personalised report.
The NHS is designed to identify and treat disease. It is not designed to optimise health, prevent future illness, or explain vague symptoms. This is not a criticism — it is a structural reality of a system that serves 67 million people with limited resources. But it means that if you go to your GP feeling tired, gaining weight, losing hair, struggling with mood, or experiencing any of the common symptoms that drive people to seek answers, the testing you receive will be narrow by design.
What your GP actually tests and what it catches:
A full blood count checks haemoglobin, red cells, white cells, and platelets. It catches anaemia, infection, and some blood cancers. It does not catch iron depletion before anaemia develops, which is the stage where most symptoms begin.
Basic kidney function checks creatinine and eGFR. It catches established kidney disease. It does not catch early kidney changes detectable by cystatin C, nor does it check uric acid which indicates gout risk and metabolic dysfunction.
Liver function checks ALT and sometimes ALP and bilirubin. It catches active liver damage. It does not catch early fatty liver which is better detected by GGT in combination with ALT, or metabolic dysfunction driving liver stress.
TSH checks whether the pituitary gland thinks the thyroid is working. It catches overt hypothyroidism and hyperthyroidism. It does not catch poor T4-to-T3 conversion, subclinical thyroid dysfunction, or autoimmune thyroid disease. Free T3, Free T4, and thyroid antibodies are needed for the complete picture.
Fasting glucose catches diabetes. It does not catch insulin resistance, which develops 5-10 years before glucose becomes abnormal. Fasting insulin and HOMA-IR catch insulin resistance early. HbA1c provides a 2-3 month glucose average that is more reliable than a single fasting reading.
What your GP does not test and what it would catch:
Ferritin below 50 in a woman presenting with fatigue. Missed because the lab range starts at 10-13. Would catch functional iron depletion driving fatigue, headaches, hair loss, and exercise intolerance.
Free T3 below range in a patient with fatigue and normal TSH. Missed because GPs do not test Free T3. Would catch impaired thyroid conversion driving fatigue, weight gain, brain fog, and cold intolerance.
Vitamin D at 38 nmol/L. Missed because many GPs do not routinely test vitamin D and the NHS threshold of 25 nmol/L is set at the disease-prevention level, not the optimal health level. Would catch deficiency contributing to fatigue, low mood, poor immunity, and bone health risk.
Cortisol above range in a stressed professional. Not tested unless Cushing's syndrome is suspected. Would catch chronic physiological stress driving fatigue, abdominal weight gain, poor sleep, and suppressed reproductive hormones.
Fasting insulin at 22 mIU/L with normal glucose. Not tested in standard screening. Would catch insulin resistance 5-10 years before diabetes diagnosis, when dietary intervention is most effective.
Testosterone at the lower end of normal in a man with fatigue and low libido. Possibly tested but without SHBG, free androgen index, or LH/FSH, making the result uninterpretable in isolation.
ApoB elevated with normal total cholesterol. Not tested in standard lipid panels. Would catch elevated cardiovascular risk that LDL cholesterol alone can miss. Many cardiologists now consider ApoB the single most important cardiovascular marker.
Lipoprotein(a) genetically elevated. Never tested in standard NHS care despite being an independent risk factor for heart attack and stroke affecting 1 in 5 people. Everyone should know their Lp(a) at least once.
Cancer markers (CEA, CA 19-9, PSA, CA-125). Not tested in asymptomatic screening through the NHS. The TrueVitals Ultimate panel includes them as baseline markers for monitoring.
Anti-tTG IgA for coeliac disease. Not routinely tested despite coeliac affecting an estimated 1 in 100 people, with the majority undiagnosed. Would catch a treatable condition that causes fatigue, bloating, nutritional deficiencies, and malabsorption.
The gap between "normal" and "optimal":
Perhaps the most important difference between NHS testing and comprehensive private testing is the interpretation framework. NHS reference ranges are based on 95% of the general population — a population that includes people who are overweight, sedentary, chronically stressed, and nutritionally depleted. Falling within this range means you are not clinically abnormal compared to the average person. It does not mean you are optimal for your age, sex, and activity level.
Private comprehensive testing with optimal ranges compares your results against the narrower range associated with the best health outcomes for your specific demographic. A ferritin of 14 is "normal" by NHS standards but functionally depleted by optimal standards. A vitamin D of 38 is "adequate" by NHS standards but deficient by optimal standards. A Free T3 of 3.4 is at the bottom of the range by NHS standards but below optimal for cellular energy production.
The TrueVitals 60-page personalised report uses both normal and optimal ranges for every biomarker, colour-coded so you can see at a glance where you sit. Markers that fall within the lab range but outside the optimal range are flagged and explained in the context of your symptoms and lifestyle. This is the information your GP cannot provide.
See what this looks like in a real report →