The question is never “is this test accurate?” — most are. It is what will you do differently once you have the result, and what happens if it is abnormal for no reason. A test that cannot change a decision is not neutral; it costs money, time and often peace of mind.
1. Blood tests, one at a time
| Test | Verdict |
|---|---|
| Lipid profile | Worth having. From 40 via the Health Check, earlier with family history. Ask for non-HDL cholesterol rather than fixating on total, and see apoB if you want the better particle measure |
| Lp(a) | Worth having once, ever. Genetically set, does not need repeating, and identifies a substantially higher-risk group who otherwise look ordinary. One of the few genuinely underused tests |
| HbA1c | Worth having where risk factors exist. Detects the pre-diabetic range, which is the point at which it is still reversible |
| Kidney function and electrolytes | Worth having if you take an ACE inhibitor, ARB or diuretic — that is what the monitoring is for. Not otherwise, in a well person |
| Liver function | Conditional. Useful where there is a reason. In a well person, mildly raised ALT is common and usually reflects fatty liver rather than disease — see the liver chapter, where the answer is a lifestyle one rather than a further test |
| Thyroid (TSH) | Worth having if symptomatic, and symptoms are routinely misattributed to menopause, ageing or low mood. Not worth routine repetition when normal. Subclinical abnormalities are common and mostly do not need treating |
| Full blood count | Worth having if tired, bleeding or unwell. Anaemia is a symptom needing a cause, not a signal to buy iron — iron deficiency in an adult man or a postmenopausal woman needs investigating, not supplementing |
| Vitamin D | Usually not worth testing. UK advice is 10 µg daily from October to March for everyone, and year-round for some groups — so for most people the test does not change the action. Test where there is bone disease, malabsorption or very limited sun exposure |
| B12 and folate | Worth having on metformin, a long-term PPI, after gastric surgery, or on a vegan diet. Not routinely otherwise |
| hs-CRP | Conditional and easily over-read. Non-specific — a cold raises it. It has a place in risk refinement; it is not a general wellness marker |
| Cortisol | The right test for a specific question and the wrong one for tiredness. It diagnoses Cushing's and Addison's, both uncommon and both with distinctive features. It does not measure how stressed you are in any useful way — levels swing enormously across the day and with the act of having blood taken. "Adrenal fatigue" is not a diagnosis and testing for it produces confusion rather than answers |
| Testosterone | Conditional. Legitimate where there are genuine symptoms, measured on a morning sample and repeated before acting. The private clinic pathway straight from a single result to a prescription is the problem, not the hormone |
| Tumour markers — CA125, CEA, PSA as a panel | Not worth having as screening. Designed for monitoring known disease. Used on well people they generate far more false alarms than diagnoses. PSA is a separate conversation — available on request from 50 with a proper discussion, but there is no national programme, and that is a considered decision rather than an oversight |
| Broad micronutrient panels | Not worth having. Twenty or thirty analytes in a well person will produce an abnormal result by arithmetic alone, since reference ranges are typically set so one in twenty healthy people falls outside. Each one then needs explaining |
2. Scans and cardiac tests
| Test | Verdict |
|---|---|
| Coronary artery calcium score | Worth having in the right person — someone at intermediate risk genuinely undecided about a statin, where the result will change the decision. Not worth having if you already know the answer, and it has real limits: it is blind to soft plaque, and it cannot distinguish spotty from dense calcification. The chapter |
| Abdominal aortic aneurysm ultrasound | Worth having, and free for men at 65. One scan, minutes long, for something silent until it ruptures. Among the best-evidenced single tests in this list |
| Carotid ultrasound | Not recommended as screening in people without symptoms. Finding an asymptomatic narrowing frequently leads to intervention whose risks may exceed its benefit. Appropriate after a stroke, TIA or a bruit — a different situation |
| Resting ECG | Conditional. Cheap and useful with symptoms, palpitations, or before some drugs. As a screening test in a well adult it mostly generates non-specific abnormalities. The exception worth knowing is competitive young athletes, where screening for inherited cardiac conditions has a genuine case |
| Checking your own pulse for atrial fibrillation | Worth doing, free, and under-used from 65. AF is common, frequently silent, and anticoagulation prevents strokes. Thirty seconds with two fingers, or a device that does it for you |
| DEXA bone scan | Worth having with risk factors — a fragility fracture, early menopause, long-term steroids, or a high FRAX score. Not as a routine at a particular birthday |
| Whole-body MRI | Not worth having, and this is the strongest negative on the page. It is genuinely the mass-screening idea that sounds most reasonable and performs worst. In people without symptoms it produces incidental findings in a large proportion of those scanned, the overwhelming majority harmless — each generating follow-up imaging, sometimes biopsy, and durable anxiety. There is no evidence it extends life, and the harms are not hypothetical. If you are buying one, buy the resistance training and the blood pressure monitor instead. The scope of that verdict, because it must not be read wider than it is: it applies to self-funded whole-body screening in someone at ordinary risk. It does not apply to annual whole-body MRI surveillance in Li-Fraumeni syndrome and comparable high-risk genetic conditions, where it is guideline-recommended, arranged through clinical genetics, and a different intervention answering a different question in a group with a very high pre-test probability |
| CT for anything without a question | Not worth having. Ionising radiation, and the same incidental-findings problem |
3. The commercial tier
- "Biological age" and epigenetic clocks. Interesting research tools. Poor reproducibility between samples and between providers, no demonstrated ability to change a decision, and nothing you would do differently on the result. See the longevity industry note.
- Direct-to-consumer genetic testing. Genuinely useful for a small number of actionable findings, and misleading for polygenic risk estimates sold as destiny. Anything that would change your medical care needs confirming through a clinical laboratory, and a worrying result deserves genetic counselling rather than a forum.
- Gut microbiome panels. The science is real and the consumer product is well ahead of it. No validated normal range, poor reproducibility, and dietary advice generated from it is generic advice with a premium attached.
- Food intolerance IgG testing. No. IgG to a food indicates exposure, not intolerance. Professional bodies advise against it, and the usual outcome is an unnecessarily restricted diet.
- Annual executive health screens. A bundle of the above. The bundling is the problem — each individual test may be defensible for someone, and doing all of them on everyone guarantees findings that need chasing.
The question to ask any provider, including the NHS. What will we do
differently depending on the result? If there is no answer, or the answer is "we would repeat it in
six months", the test is not going to help you. That single question sorts almost everything on
this page, and it is the only skill this chapter is really trying to teach.