Biomarker reference
The lines a UK or US laboratory prints on a routine blood panel, in the order the report prints them, each with one plain sentence on what it actually measures. Use it to find the marker in front of you, then follow it through to the conditions it contributes to.
Marker index
Grouped the way a laboratory groups them: full blood count first, then chemistry, liver, lipids, glucose and hormones, and finally iron, vitamins and inflammation. Reference ranges differ between laboratories, so always read your own report against the range printed beside it.
Conditions
Blood tests rarely diagnose on their own. They narrow the possibilities, confirm or weaken a suspicion, and show how something is progressing, alongside your symptoms, examination and history. Each entry below names the markers a clinician tends to read together.
The commonest anaemia worldwide, and the one blood work shows most clearly: low ferritin with a small, pale red cell picture. The tests establish the deficiency, but not its cause, which is why bleeding and absorption are then looked for.
FerritinHaemoglobinMCVRDWTSAT
A large-cell anaemia with neurological symptoms that can arrive before the count changes. B12 and folate levels together with MCV point towards it, though borderline B12 often needs a second-line test to settle.
Vitamin B12Serum folateMCVHaemoglobin
Here blood work carries most of the diagnostic weight: HbA1c and fasting glucose thresholds define prediabetes and diabetes. Both still need a confirming sample, and anaemia or a haemoglobin variant can make HbA1c misleading.
HbA1cFasting plasma glucoseFasting insulinTriglycerides
A cluster of changes rather than a single disease, and blood work usually spots it years early: insulin climbing while HbA1c is still normal, triglycerides up, HDL down. Waist measurement and blood pressure complete the picture.
Fasting insulinHbA1cTriglyceridesHDL-CALT
Tiredness, weight gain and cold intolerance have many causes, so TSH with free T4 is what separates thyroid failure from the rest. TPO antibodies then indicate whether autoimmune thyroiditis is behind it.
TSHFT4TPO Ab
Suppressed TSH with raised free T4 or free T3 makes an overactive thyroid very likely, but blood work cannot say why. Distinguishing Graves disease from a nodule or thyroiditis needs antibodies and imaging.
TSHFT4FT3
Staged on eGFR calculated from creatinine, confirmed only when the reduction has persisted for three months and is read together with urine protein. A single low eGFR after illness or dehydration proves nothing.
CreatinineeGFRUreaPotassiumAdjusted calcium
Often found by accident, as a mildly raised ALT on a routine panel in someone with metabolic risk factors. Blood tests raise the suspicion and help exclude other liver disease, while imaging and fibrosis scores judge severity.
ALTASTGGTTriglyceridesHbA1c
A raised GGT with AST above ALT, sometimes alongside a large MCV, is a recognisable pattern rather than proof. Blood work supports the conversation about intake and tracks recovery once drinking stops.
GGTASTALTMCVPLT
Lipids do not diagnose heart disease; they feed a risk estimate together with age, blood pressure, smoking and family history. LDL and non-HDL set the treatment target, and Lp(a) uncovers inherited risk once.
LDL-CNon-HDLHDL-CTriglyceridesLp(a)
A high neutrophil count with a rising CRP suggests a bacterial process, while a lymphocyte pattern leans viral. Neither locates the infection, so blood work guides how urgently to look, not where.
WBCNeutLymphCRP
Persistently raised CRP or ESR with a falling albumin says inflammation is ongoing and deserves explaining. The specific diagnosis comes from autoantibodies, imaging and examination, not from these markers.
CRPESRAlbuminPLTHaemoglobin
Diagnosed from the joint, not the blood: uric acid can be normal during an attack and high in people who never have one. Levels still matter for choosing and monitoring long-term treatment.
Uric acidCreatinineeGFRCRP
Common through northern winters and largely silent, so it is found by measuring 25-hydroxyvitamin D rather than by symptoms. Calcium and ALP are read alongside it when bone pain or very low levels appear.
25(OH)DAdjusted calciumALP
Not a diagnosis but the reason most people get tested, and a basic panel covers the common reversible causes at once. A completely normal set of results is itself informative and moves the search elsewhere.
HaemoglobinFerritinTSHHbA1cVitamin B12CRP
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FAQ
A reference range is built from the middle 95% of healthy people, so one in twenty healthy results falls outside it by definition. On a panel of thirty markers, at least one flag is the statistically expected outcome. What matters is how far outside the range the value sits, whether it is drifting in one direction across repeat tests, and whether it fits your symptoms.
Each laboratory validates ranges for its own analysers, methods and local population, and UK and US labs often report in different units — haemoglobin in g/dL or g/L, glucose in mg/dL or mmol/L. That is why a value should always be read against the range printed next to it on that report, and why comparing two labs directly can mislead.
For a full blood count, liver tests, kidney tests, thyroid tests and ferritin, no. Fasting glucose and insulin require eight to twelve hours without food, and triglycerides are meaningfully raised by a recent meal. HbA1c and non-HDL cholesterol are valid at any time of day, which is why non-fasting lipid panels are now standard in much of the NHS.
A first pass normally covers full blood count, ferritin, TSH, HbA1c, kidney and liver tests, calcium, vitamin B12, folate, vitamin D and CRP. Iron deficiency, thyroid failure and undiagnosed diabetes account for a large share of cases. If all of that is clean, the cause is more likely to be sleep, mood, medication or another condition that blood work does not show.
For a few conditions it comes close: HbA1c thresholds define diabetes, and TSH with free T4 defines thyroid failure. For most, blood work narrows the possibilities and measures severity while the diagnosis rests on symptoms, examination, imaging or a biopsy. Gout is the clearest counter-example, since uric acid can be normal mid-attack.
It depends on the marker. CRP and white cells move within days, so a repeat in one to two weeks shows whether an acute process is settling. Ferritin, HbA1c and lipids change over months and are usually rechecked at three months after any treatment change. A borderline eGFR needs three months to distinguish acute from chronic kidney disease. Your clinician sets the interval.
This article is health information, not a medical diagnosis. Always discuss your results with a qualified clinician.