A blood test result arrives as a column of abbreviations and numbers, with a reference range beside each one and no explanation of what any of it is for.
This is a guide to what a standard UK panel is actually asking, so you can read your own results and know which questions are worth taking back to your GP.
One rule before anything else. A result outside the reference range is not a diagnosis, and a result inside it is not a clean bill of health. Reference ranges are typically set so that 95% of a healthy population falls inside — which means one in twenty healthy people sits outside a given range by definition. On a panel of twenty markers, having something flagged is the norm, not the exception.
Full blood count (FBC)
The most commonly ordered test, looking at the cells rather than the chemistry.
Haemoglobin (Hb). Oxygen-carrying capacity. Low means anaemia, and the important question is always why — iron deficiency, B12 or folate deficiency, blood loss, or chronic disease. In adults, unexplained iron deficiency anaemia is investigated rather than simply supplemented, because it can indicate bleeding somewhere.
MCV. The average size of red cells, and the most useful clue to the cause. Small cells point towards iron deficiency; large cells towards B12 or folate deficiency, alcohol, or thyroid problems.
White cell count. Immune cells. Raised often means infection or inflammation. A recent virus can shift it, so a single result is interpreted in context.
Platelets. Clotting cells. Both extremes matter, and both are followed up rather than acted on immediately.
Kidney function (U&E)
Creatinine and eGFR. Creatinine is muscle breakdown product cleared by the kidneys; eGFR is the calculated estimate of filtration rate derived from it.
Two things worth knowing. Muscle mass affects creatinine — a very muscular person can have a raised creatinine and entirely normal kidney function. And creatine supplementation raises it too, which is why the creatine article suggests mentioning it before a blood test.
eGFR declines gradually with age, and a mildly reduced value in an older person is not automatically disease.
Sodium and potassium. Electrolytes. Abnormalities are usually related to medication, hydration or other conditions rather than being a problem in themselves. Potassium in particular is worth attention because several common drugs affect it.
Liver function (LFT)
ALT and AST. Enzymes released when liver cells are damaged. Mildly raised ALT is extremely common and the most frequent cause is fatty liver associated with weight and metabolic factors — increasingly labelled MASLD. Alcohol, medications and viral hepatitis are the other main causes.
Mild elevation is usually rechecked before anything else happens.
ALP and GGT. These point towards the bile ducts. GGT is sensitive to alcohol, which is why it is sometimes used to corroborate history, though it rises for other reasons too.
Albumin and bilirubin. Synthetic function and processing. Gilbert’s syndrome, a harmless inherited variant, raises bilirubin in a few percent of people and causes lifelong mild flagging of an otherwise irrelevant number.
Lipids
Total cholesterol, HDL, non-HDL, LDL, triglycerides.
The number that matters most for risk is non-HDL cholesterol — everything atherogenic, calculated as total minus HDL. UK risk tools use it, and it does not require fasting.
Triglycerides are the one component genuinely affected by a recent meal, and raised levels sit alongside insulin resistance and metabolic syndrome.
HDL is the one where the simple story has broken down. It was called “good cholesterol” on the basis of observational data, but drugs that raise it have not reduced cardiovascular events, and very high levels are not protective. Treat it as a risk marker, not a target.
For why ApoB may be the better measure than any of these, see the separate article in this section.
Glucose
HbA1c — three-month average glucose. Below 42 mmol/mol normal, 42–47 prediabetes, 48 and above diagnostic of type 2 diabetes on confirmation. Covered in its own article, because it is the single most forward-looking number on a standard panel.
Fasting glucose is a snapshot and interpreted differently.
Thyroid
TSH, sometimes with free T4. TSH is the pituitary’s instruction to the thyroid, so it moves in the opposite direction to thyroid activity — a high TSH suggests an underactive thyroid.
Symptoms of thyroid dysfunction overlap heavily with the general experience of being tired in midlife, which is why it is tested often and why a normal result is useful information.
The ones people ask about
Ferritin. Iron stores. Low means iron deficiency even before anaemia appears. But ferritin also rises with inflammation, so a normal value in someone unwell does not exclude deficiency — this is a common source of confusion.
Vitamin B12 and folate. Deficiency causes anaemia and neurological symptoms. B12 deficiency becomes more common with age as absorption declines, and metformin is associated with lower levels.
Vitamin D. Widely measured, and routine testing of the general population is not recommended. Given that UK guidance suggests supplementation for everyone in winter regardless, the test rarely changes what you should do.
CRP. A general inflammation marker. Raised for any of dozens of reasons, from a cold to arthritis. High-sensitivity CRP is used in some cardiovascular risk assessment, but a one-off result in an otherwise well person is mostly noise.
How to read your own results usefully
Keep them. Every one, in one place. The trend across years is more informative than any single value, and nobody else is systematically tracking it for you. A number drifting steadily within the normal range is information you will otherwise lose.
Look at the direction, not just the flag. Creatinine rising from 70 to 95 across five years is worth mentioning, even though both are normal.
Ask about anything flagged, and ask what happens next. Sometimes the answer is a repeat test in three months, and knowing that is the plan prevents a lot of anxiety.
Do not diagnose yourself. Interpretation depends on your history, medication, symptoms and the pattern across markers. One number, read alone, on the internet, is the specific situation in which people frighten themselves for no reason.
Why this matters here
Almost everything that shortens healthy life expectancy develops silently over decades. A blood panel is one of the few routine encounters with that process before it announces itself.
Which is why the single most valuable habit in this article is the least clinical one: keep your results, and look at the direction of travel. The reference range tells you where you sit against the population. Your own history tells you where you are going.
This article is for general information and is not medical advice. Discuss your results with your GP, who has your full history and context. Do not start, stop or change any treatment on the basis of anything here.
Sources
- NICE. Type 2 diabetes in adults: management (NG28); Cardiovascular disease: risk assessment and reduction (CG181).
- HbA1c diagnostic thresholds, UK reference ranges. https://www.boltpharmacy.co.uk/guide/hba1c-diabetes-cut-off
- Sniderman AD, et al. Discordance among apoB, non–high-density lipoprotein cholesterol, and triglycerides. European Heart Journal, 2024;45(27):2410–2418.
- Scientific Advisory Committee on Nutrition. Vitamin D and health, 2016.
- Candow DG, Forbes SC, et al., on creatine supplementation and plasma creatinine. Nutrients, 2021;13(6):1912.
This article is for general information and is not medical advice. If a health problem is affecting your daily life, speak to your GP.
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