Cholesterol blood test: what it measures and what can change it
Total cholesterol is all the cholesterol in the blood: the 'good' HDL plus the rest.
General information about the test, from Hea's guide and the NHS · Last reviewed 5 November 2026
What it measures, and why GPs check it
Total cholesterol
Total cholesterol is all the cholesterol in the blood: the 'good' HDL plus the rest.
With HDL it feeds QRISK3, the 10-year heart and stroke risk score UK GPs use.
LDL cholesterol
LDL is the cholesterol that builds up in artery walls. Many reports calculate it from the other values rather than measure it, and it cannot be worked out when triglycerides are very high.
Statin treatment is aimed at it, and very high values point to an inherited condition.
HDL cholesterol
HDL carries cholesterol back to the liver; reports often call it the 'good' cholesterol.
It is one of the two numbers the NHS Health Check needs to calculate heart risk.
Triglycerides
Triglycerides are fat carried in the blood. The last meal and alcohol change the number a lot.
Very high values carry a risk of pancreatitis; middle values make the heart risk calculator less reliable.
Levels in UK guidance
Ranges differ between labs — your report shows your lab's range.
Total cholesterol
- NHS pages give below 5.0 mmol/L as the healthy level quoted for adults. NHS.uk, high cholesterol (2026)
- Above 7.5 mmol/L with early heart disease in the family is where NICE asks the GP to think about familial hypercholesterolaemia, an inherited condition. NICE CG71 1.1.1
- Above 9.0 mmol/L, or non-HDL cholesterol above 7.5 mmol/L, NICE asks for specialist advice. NICE NG238 1.4.5, 1.4.8
LDL cholesterol
- Below 3.0 mmol/L is the level Lab Tests Online UK gives as healthy for adults. Lab Tests Online UK: Lipid profile; Cholesterol test
- For people taking a statin without heart disease NICE follows non-HDL cholesterol (a fall of more than 40%); with heart disease it sets a target in LDL (2.0 mmol/L or less) or non-HDL (2.6 or less). NICE NG238 (2023), recs 1.6.1, 1.7.1
HDL cholesterol
- NHS pages quote above 1.0 mmol/L for men and above 1.2 mmol/L for women as the healthy level. NHS.uk, high cholesterol (2026)
- A low HDL raises the calculated risk score, but guidelines do not treat HDL itself: nothing is prescribed to raise it. NICE NG238
Triglycerides
- Fasting below 1.7 mmol/L is the usual reported range; a non-fasting sample is read a little higher. NHS.uk; EAS/EFLM 2016
- Between 4.5 and 9.9 mmol/L, NICE notes the risk calculator may underestimate the risk. NICE NG238 1.4.8
- 10–20 mmol/L: NICE asks for a repeat fasting sample in 5 days to 2 weeks. Above 20 mmol/L not explained by alcohol or poorly controlled diabetes: urgent specialist referral. NICE NG238 1.4.6–1.4.7
What can shift the number
Before the test
- Ate in the 8 hours before. NICE does not ask for fasting before a cholesterol test. After a usual meal triglycerides read a little higher on average, and total and LDL cholesterol a little lower; LDL is sometimes worked out from them. NICE NG238 Cardiovascular disease: risk assessment and reduction, including lipid modification (2023), Terms used: full lipid profile, and rec 1.4.7; EAS and EFLM consensus on non-fasting lipids (2016; PMID 27122601)
Now or in the last 3 months
- Pregnant. In pregnancy the usual ranges for many tests are different: show these results to your midwife or GP. NICE NG201 Antenatal care (2021); NICE NG3 Diabetes in pregnancy (2015, updated 2020); RCOG Green-top Guideline 76: thyroid disorders in pregnancy (2025; PMID 40240075); NICE NG239 (2024) rec 1.3.2; BSG guidelines on the management of abnormal liver blood tests (2018); Lab Tests Online UK: Lipid profile; C-reactive protein (CRP); ESR
- Had a baby or a pregnancy loss in the last 12 months. Cholesterol and triglycerides are high in pregnancy: Lab Tests Online UK advises waiting at least three months after the birth before a cholesterol test. Lab Tests Online UK: Lipid profile; HEART UK: Pregnancy and blood fats
- An infection or illness in the 6 weeks before. Cholesterol can read lower or higher than usual during or just after an illness: Lab Tests Online UK advises waiting at least six weeks. Lab Tests Online UK: Lipid profile; NHS.uk: Cholesterol levels
Long-term conditions
- Diabetes. QRISK3 counts type 1 and type 2 diabetes separately; NICE uses no risk score in type 1, and poorly controlled diabetes raises triglycerides. QRISK3 (Hippisley-Cox 2017; PMID 28536104), box 1; NICE NG238 (2023), recs 1.1.8, 1.1.9, 1.4.3
- High blood pressure. QRISK3, the score a GP reads cholesterol in, takes the top blood pressure number and whether the person is treated for high blood pressure. QRISK3 (Hippisley-Cox 2017; PMID 28536104), box 1; NICE NG238 (2023), rec 1.5.5
- Heart disease or a stroke. With known heart or circulation disease NICE uses a target (LDL 2.0 mmol/L or less, or non-HDL 2.6 or less), not a risk score. NICE NG238 (2023), recs 1.7.1, 1.1.7
- A thyroid condition, or thyroid surgery or radioiodine in the past. An underactive thyroid raises cholesterol; NICE lists it among the common causes to rule out before a referral for raised blood fats. NICE NG238 (2023), recs 1.4.3, 1.5.5; Lab Tests Online UK: Cholesterol test
- Kidney disease. With reduced kidney function or protein in the urine NICE does not use a risk score: the risk is already counted as high. NICE NG238 (2023), recs 1.1.9, 1.8.1
Some medicines and supplements can change this result too. When you add your results, Hea asks which ones you take.
What a GP reads it with
Total cholesterol
Read together with: HDL cholesterol, Blood pressure (upper). NICE NG238 Cardiovascular disease: risk assessment and reduction, including lipid modification (2023), recs 1.1.7, 1.4.1; QRISK3 (Hippisley-Cox 2017; PMID 28536104), box 1
A GP usually calculates QRISK3 with age, blood pressure and other factors, talks about food, activity and smoking, and discusses a statin when the 10-year risk is 10% or higher.
LDL cholesterol
Read together with: Total cholesterol, HDL cholesterol, Triglycerides. NICE NG238 (2023), Terms used: full lipid profile; Lab Tests Online UK: Lipid profile
A GP usually puts it into the risk score, checks whether the sample was fasting, and repeats the panel before changing anything.
HDL cholesterol
Read together with: Total cholesterol. NICE NG238 (2023), rec 1.4.1; QRISK3 (Hippisley-Cox 2017; PMID 28536104), box 1
A GP usually reads it inside QRISK3 rather than on its own; activity, stopping smoking and weight are what move it.
Triglycerides
Read together with: Total cholesterol, HDL cholesterol, HbA1c, TSH, ALT, eGFR. NICE NG238 (2023), rec 1.4.3
A GP usually repeats the sample fasting, asks about alcohol and sugary drinks, and looks at blood sugar at the same time.
Questions to ask your GP
- What is my QRISK3 score with these numbers?
- Should anyone in my family be tested?
- When should the lipids be repeated?
- Was this calculated or measured directly?
- Does my family history change what this means?
- What would make you suggest treatment?
- How does this number change my overall risk?
- Which part of my results is worth acting on first?
- Should I repeat this fasting?
- Could my alcohol or diet explain this?
Safety first
If your lab or GP has flagged your result as urgent, follow their advice first.
Not for emergencies: call 999 or NHS 111.
Questions people ask
What should your cholesterol level be?
NHS pages give these levels as a guide for healthy adults: total cholesterol below 5 mmol/L, and HDL above 1.0 mmol/L for men or above 1.2 mmol/L for women. Your GP uses your cholesterol together with your age, blood pressure and health conditions. From these they may work out a QRISK score, an estimate of your chance of a heart or circulation problem over the next 10 years.
NHS: High cholesterol – cholesterol levels, Page last reviewed 13 March 2026What does a cholesterol test measure?
A cholesterol test can measure total cholesterol, HDL ('good') cholesterol and non-HDL cholesterol, which is the difference between the two. You may only be told your total cholesterol. You might be able to get the separate results too.
NHS: High cholesterol – cholesterol levels, Page last reviewed 13 March 2026Do you need to fast before a cholesterol test?
Most people do not need to fast. The NHS says you might be asked not to eat anything for up to 12 hours before the test, so follow what your GP surgery tells you. The blood is usually taken from your arm, or from a finger-prick during an NHS Health Check.
NHS: High cholesterol – getting tested, Page last reviewed 13 March 2026What are the symptoms of high cholesterol?
High cholesterol does not usually cause symptoms. The NHS says you can only find out if you have it from a blood test. It can be caused by fatty food, not exercising enough, being overweight, smoking and drinking alcohol, and it is more likely if it runs in your family.
NHS: High cholesterol, Page last reviewed 13 March 2026How can I lower my cholesterol?
The NHS advises cutting down on fatty food, especially foods high in saturated fat such as fatty meat, sausages, butter, cream, cheese, cakes and biscuits. Eat more oily fish, wholegrains, nuts and seeds, fruit and vegetables, and be more active. Stopping smoking and drinking less alcohol help too. Some people also need medicine, as their GP advises.
NHS: How to lower your cholesterol, Page last reviewed 13 March 2026Got your result? Start with this question in your AI.
Join Hea, add it to Claude or ChatGPT, and your chat opens with this question ready. Hea shows what the lab printed, your past results and what can shift a number; your GP decides what it means for you.
Hea, my cholesterol result came back — help me understand it with my history
Closed beta for adults (18+) living in the UK. Free in the beta.
Sources
Each line about the test above names the guideline it comes from, as Hea's guide cites it. The answers to the questions come from:
- NHS: High cholesterol – cholesterol levels, Page last reviewed 13 March 2026
- NHS: High cholesterol – getting tested, Page last reviewed 13 March 2026
- NHS: High cholesterol, Page last reviewed 13 March 2026
- NHS: How to lower your cholesterol, Page last reviewed 13 March 2026