Some blood tests get mentioned at a GP appointment, noted down, and then quietly left for another year. Not because they are complicated, but because there is no pain pushing them up the list. Five of them come up again and again: PSA, HbA1c, cholesterol, sexual health screens and thyroid function. This short guide looks at the blood tests people put off, what each one actually measures and how the sample is collected through London Medical Laboratory (LML).
Why these blood tests get put off
The five have something in common: what they measure often gives no signal you can feel. The NHS notes that high cholesterol does not usually cause symptoms and can only be found with a blood test. It says the same about sexually transmitted infections: many have no symptoms, and the only way to know for sure is to get tested. LML's own description of HbA1c points out that over a million people in the UK have diabetes and do not know it. When nothing hurts, a test is easy to postpone.
None of this means something is wrong. A result within the reference range is the most common outcome, and it is useful in its own right: it gives you and your doctor a baseline to compare against later.
PSA (Prostate Specific Antigen)
PSA is a protein made by the prostate gland. The Prostate Specific Antigen (Total) test measures its level in the blood. LML is clear that the test is not specific to prostate cancer: a raised level can also come from non-cancerous conditions such as an enlarged prostate or prostatitis, and age, family history and some medicines also affect it.
The NHS explains that routine PSA testing is not currently offered, that men and anyone with a prostate can ask a GP about it, and that the doctor will talk through the benefits and risks first. A large review of the randomised trials found that screening probably makes no difference to overall mortality and may have a small effect on prostate cancer deaths, which is why the decision is usually an individual one (Ilic et al., 2018).
Preparation matters. For 48 hours before a PSA test, the NHS advises against ejaculation, anal sex, cycling and exercise that leaves you out of breath, because these can raise the level. You can eat and drink as usual.
HbA1c
HbA1c, listed in the catalogue as Diabetes (HbA1c), reflects how much glucose has attached to the haemoglobin in red blood cells. LML describes it as the gold standard test for diabetes and its monitoring, and a laboratory guideline from the American Diabetes Association lists it, alongside glucose, among the tests used to classify and follow diabetes (Sacks et al., 2023).
The NHS notes that not everyone with type 2 diabetes has symptoms, and that the risk is higher if you are white and over 40, or over 25 and from a South Asian, Chinese, Black African or Black Caribbean background, if a parent or sibling has it, or if you have high blood pressure. LML says this test can be done on a finger-prick home sample or a phlebotomy sample.
Cholesterol
The Cholesterol Lipid Profile measures seven values: total cholesterol, HDL, LDL, non-HDL cholesterol, triglycerides, the total cholesterol to HDL ratio and the HDL percentage. The NHS suggests asking for a cholesterol test if you have never had one and you are over 40, overweight, or high cholesterol or heart problems run in your family.
A common reason to delay is the idea of a long fast. The NHS says you might be asked not to eat for up to 12 hours, but most people do not need to fast. LML runs this profile on a finger-prick home sample or on a phlebotomy sample.
