Last updated 24 October 2026.
A blood test can put a number on inflammation. The harder part is knowing what that number can and cannot tell you.
Inflammation markers are substances in your blood that rise when the body is inflamed. The most widely used is C-reactive protein, or CRP. A result below 10 mg/L usually means there is no clinically active inflammation, while a higher result points to infection or inflammation without saying what is causing it (Lab Tests Online UK).
This guide explains how the main markers differ, what normal and high results mean, how CRP relates to ageing, how to get tested, and what the research says about lifestyle.
Ageing is partly a story about low-level inflammation that never quite switches off. Researchers call it inflammaging, and it is one of the best-described features of how we age (Franceschi et al., 2018). One major review explains that most older adults develop raised blood inflammatory markers, which are linked with a higher risk of chronic disease, disability, frailty and earlier death (Ferrucci and Fabbri, 2018).
That is why markers such as CRP interest anyone who thinks about longevity. Not how long you live, but how many of those years you spend capable and independent. Inflammation sits at the centre of the five systems that shape healthspan. A marker is a signal, though, and not a verdict. It only helps when you know what it can show.
Inflammation markers are measurable signs in your blood that the immune system is active. Inflammation itself is not the enemy. It is how your body responds to infection and injury. The question is whether it switches off when the job is done.
Tests do not measure inflammation directly. They measure proteins that the body makes more of when inflammation is present. CRP is made by the liver and released into the blood within a few hours of tissue injury (Lab Tests Online UK). Other markers rise by different routes, which is why doctors sometimes use more than one.
CRP and hs-CRP measure the same molecule. The difference is the question being asked. A standard CRP test looks for the higher levels seen with infection or inflammatory disease. A high-sensitivity CRP test, known as hs-CRP, picks up much smaller amounts and may be requested for people who seem healthy, to help assess heart disease risk. hs-CRP is not widely used (Lab Tests Online UK).
CRP also moves quickly. After an acute trigger such as an infection, it can rise above 5 mg/L within about six hours and peak at around 48 hours. Its half-life is about 19 hours, so it falls rapidly once the trigger has gone (Pepys and Hirschfield, 2003). Low-grade chronic inflammation looks different. It is a small, steady rise that does not settle. The diagram shows the idea.
This is why one reading can mislead. A recent infection or injury can push a result up even when your usual level is low (Pearson et al., 2003).
CRP is not the only blood test used to check for inflammation. The NHS describes ESR, short for erythrocyte sedimentation rate, and CRP as blood tests that can be used to check levels of inflammation in the body. They are usually done together, and they can differ. In polymyalgia rheumatica, for example, a normal ESR with a raised CRP is more likely to point towards the condition. High levels do not automatically mean any one condition, because inflammation is a feature of many (NHS).
Researchers also measure interleukin 6, known as IL-6, which is a signalling protein, and fibrinogen, which is a blood protein. They appear often in studies of ageing and heart disease, but less often in routine tests.
| Marker | What it is | Where you are most likely to meet it |
|---|---|---|
| CRP | A protein made by the liver that rises within hours of injury or infection | GP and hospital blood tests (Lab Tests Online UK) |
| hs-CRP | The same protein, measured to detect smaller amounts | Heart risk assessment in people who seem healthy (Lab Tests Online UK) |
| ESR | A blood test often done alongside CRP to check for inflammation | GP blood tests, for example when polymyalgia rheumatica is suspected (NHS) |
| IL-6 and fibrinogen | A signalling protein and a blood protein linked to inflammation | Mostly research studies (Emerging Risk Factors Collaboration, 2010; Irwin et al., 2016) |
There is no single normal CRP number, because laboratories set their own ranges. Your report will show the range for the lab that ran your test, and your GP will read it alongside your symptoms.
Two reference points come up often. Lab Tests Online UK says that when results fall below 10 mg/L you no longer have clinically active inflammation. For hs-CRP, a statement from the American Heart Association and the Centers for Disease Control grouped results into relative heart risk bands (Pearson et al., 2003).
| Result | What it usually suggests | Source |
|---|---|---|
| Under 10 mg/L on a standard CRP test | No clinically active inflammation | Lab Tests Online UK |
| Under 1 mg/L on hs-CRP | Lower relative heart risk band | Pearson et al., 2003 |
| 1 to 3 mg/L on hs-CRP | Average relative heart risk band | Pearson et al., 2003 |
| Over 3 mg/L on hs-CRP | Higher relative heart risk band | Pearson et al., 2003 |
| 10 mg/L or more | Look for a source of infection or inflammation, then repeat the test in about two weeks | Pearson et al., 2003 |
A high result tells you something is going on. It does not tell you what. The statement advised looking for an obvious source of infection or inflammation at 10 mg/L, then discarding that result and measuring again in about two weeks. It also advised that anyone with an active infection, systemic inflammation or trauma should not be tested for heart risk until it settles, and that the whole adult population should not be screened with hs-CRP (Pearson et al., 2003).
Context matters too. A pooled analysis of 54 studies and 160,309 people with no previous vascular disease found that higher CRP was linked with higher risk of coronary heart disease, stroke and death. The link weakened, but did not disappear, once conventional risk factors were taken into account (Emerging Risk Factors Collaboration, 2010). In practice, CRP adds some information. It is not a stand-alone score.
CRP is the inflammation marker many people meet first, and it gives a rough window onto inflammaging. The causes proposed for inflammaging include central obesity, changes in the gut barrier, senescent cells and mitochondrial dysfunction (Ferrucci and Fabbri, 2018). Several of these are shaped by how you live. The picture also differs between women and men, which we cover in inflammation during menopause and men's healthy ageing.
There are honest limits. CRP is an association, not a clock. A higher value does not mean you are ageing faster, and a lower one does not mean you are not. Whether reducing inflammation improves outcomes in the conditions linked to it is still debated (Ferrucci and Fabbri, 2018). Think of CRP as one signal among many, alongside biological age markers, strength, sleep and how you feel.
The usual route is your GP, and it usually starts with symptoms. A doctor may request CRP when they suspect an inflammatory disorder or an infection (Lab Tests Online UK). ESR and CRP are often requested together (NHS). hs-CRP for heart risk is not widely used (Lab Tests Online UK).
Some private providers and clinics also offer CRP or hs-CRP as part of wider health panels. If you choose one, treat the result as the start of a conversation and not a diagnosis. Take the report to your GP if the number is high or if you have symptoms.
A few habits make a result easier to read.
The best-studied levers are the ones that already sit at the foundation of longevity. Effects in trials are usually modest and differ between people. Treat them as ways to support your biology, not as a way to chase a number.
| Factor | What studies looked at | What they found |
|---|---|---|
| Sleep | A meta-analysis of cohort studies and sleep deprivation experiments | Sleep disturbance was associated with higher CRP and IL-6, and shorter sleep with higher CRP. Effect sizes were small (Irwin et al., 2016) |
| Food | 17 trials of the Mediterranean diet in 2,300 adults, each lasting 12 weeks or more | hs-CRP was lower by about 0.98 mg/L on average, with large differences between trials (Schwingshackl and Hoffmann, 2014) |
| Exercise | 83 controlled trials with 3,769 people | Exercise training was associated with lower CRP, with a small to moderate effect (Fedewa et al., 2017) |
| Body weight | The same exercise analysis | CRP fell more when BMI also fell, and still fell a little when it did not (Fedewa et al., 2017) |
| Smoking | A review of CRP in smokers and former smokers | Researchers have studied CRP as a way to understand disease risk in this group (Tonstad and Cowan, 2009) |
Sleep is worth a closer look, because both ends of the range appeared in the data. The review also found that the extreme of long sleep was associated with higher CRP (Irwin et al., 2016). These are associations, so they do not prove that sleep changes CRP on its own.
If you smoke, stopping is one of the most useful things you can do for your health, and the NHS offers free support to help.
Supplements are not a route to a lower CRP number. Some ingredients have been studied for inflammation markers, and results vary. No authorised health claim in Great Britain covers inflammation markers. If you want to see the evidence ingredient by ingredient, we have looked at CoQ10, astaxanthin and joint supplements.
Daily Vitals sits alongside the foundations above, as one simple daily step. Daily Vitals makes no claim about CRP or any other inflammation marker, and it is not a treatment for a high result. You can see every ingredient on our ingredients page. Feel better now. Age better later.
See your GP rather than relying on tests you arrange yourself if you have a persistent fever, unexplained weight loss, ongoing pain or stiffness, swollen joints or any new symptom that worries you. A raised CRP cannot say what is wrong. Your GP can put it in context.
Do not stop or change prescribed medicines because of a test result. Speak to your GP or pharmacist before starting any new supplement if you take prescription medicines, are pregnant, trying to conceive or breastfeeding, or have a medical condition.
It depends on the laboratory, so check the range on your report. As a guide, Lab Tests Online UK says that below 10 mg/L there is no clinically active inflammation. For hs-CRP, under 1 mg/L falls in the lower relative heart risk band (Pearson et al., 2003).
It means there is likely to be inflammation or infection somewhere in the body, but not where or why. A result of 10 mg/L or more usually leads to a search for an obvious cause and a repeat test (Pearson et al., 2003). Your GP will read it alongside your symptoms.
They measure the same molecule (Lab Tests Online UK). The hs-CRP test is more sensitive to small amounts and is used to help assess heart disease risk in people who seem healthy.
Yes. CRP can rise above 5 mg/L within about six hours of an acute trigger (Pepys and Hirschfield, 2003). That is why it is best to test when you are well.
CRP has a half-life of about 19 hours and falls rapidly once the trigger has gone (Pepys and Hirschfield, 2003). If a result is high, a repeat test in about two weeks is the usual advice (Pearson et al., 2003).
Trials suggest that regular exercise and a Mediterranean-style diet are associated with lower CRP, and that weight loss adds to the effect (Schwingshackl and Hoffmann, 2014; Fedewa et al., 2017). The changes are modest, and lowering a number is not the goal. Feeling well and staying capable is.
Not necessarily. The guidance behind hs-CRP advised against screening the whole adult population (Pearson et al., 2003). Speak to your GP if you are thinking about your heart risk.
Keep reading
Longevity, healthspan and the inflammation epidemic
What is longevity, and what role does inflammation play?
CoQ10 benefits and longevity
References
Emerging Risk Factors Collaboration, Kaptoge, S. et al. (2010). C-reactive protein concentration and risk of coronary heart disease, stroke, and mortality, an individual participant meta-analysis. The Lancet, 375(9709), 132–140. doi.org
Fedewa, M.V., Hathaway, E.D. and Ward-Ritacco, C.L. (2017). Effect of exercise training on C reactive protein, a systematic review and meta-analysis of randomised and non-randomised controlled trials. British Journal of Sports Medicine, 51(8), 670–676. doi.org
Ferrucci, L. and Fabbri, E. (2018). Inflammageing, chronic inflammation in ageing, cardiovascular disease, and frailty. Nature Reviews Cardiology, 15(9), 505–522. doi.org
Franceschi, C. et al. (2018). Inflammaging, a new immune-metabolic viewpoint for age-related diseases. Nature Reviews Endocrinology, 14, 576–590. doi.org
Irwin, M.R., Olmstead, R. and Carroll, J.E. (2016). Sleep disturbance, sleep duration, and inflammation, a systematic review and meta-analysis of cohort studies and experimental sleep deprivation. Biological Psychiatry. doi.org
Lab Tests Online UK. C-reactive protein (CRP). labtestsonline.org.uk
NHS. Polymyalgia rheumatica, diagnosis. nhs.uk
Pearson, T.A. et al. (2003). Markers of inflammation and cardiovascular disease, application to clinical and public health practice. A statement for healthcare professionals from the Centers for Disease Control and Prevention and the American Heart Association. Circulation, 107(3), 499–511. doi.org
Pepys, M.B. and Hirschfield, G.M. (2003). C-reactive protein, a critical update. Journal of Clinical Investigation, 111(12), 1805–1812. jci.org
Schwingshackl, L. and Hoffmann, G. (2014). Mediterranean dietary pattern, inflammation and endothelial function, a systematic review and meta-analysis of intervention trials. Nutrition, Metabolism and Cardiovascular Diseases, 24, 929–939. doi.org
Tonstad, S. and Cowan, J.L. (2009). C-reactive protein as a predictor of disease in smokers and former smokers, a review. International Journal of Clinical Practice, 63(11), 1634–1641. doi.org
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