Low-grade inflammation is a quiet, continuous activation of the immune system, with no redness, no swelling and no fever. On a blood test it shows as a high-sensitivity CRP between roughly 1 and 3 mg/L, sometimes higher. A routine panel will not find it, because the routine panel measures a blunter version of the same protein.
You are tired in a way that sleep does not repair. Your knees are stiff for the first twenty minutes of the morning. Your GP runs bloods, everything comes back within range, and the conversation ends there. That answer can be correct and still miss what is happening, because the marker that would have shown something was never requested. Below: what the marker is, how to read it, what the trials say shifts it, and where the NHS will not help.
What counts as low-grade inflammation
Inflammation is not the enemy. Cut a finger and the tissue floods with immune cells, turns red, swells, hurts, then repairs and shuts down. That whole sequence is the acute inflammatory response doing exactly what it evolved to do. Acute inflammation has an end.
Low-grade inflammation is the same machinery running at a fraction of the intensity and never switching off. You will see it written as low grade inflammation, chronic low-grade inflammation or silent inflammation, and all three describe the same state. A 2025 review in Physiology puts it plainly: the term low-grade describes an inflammatory process that stays below the threshold for producing obvious clinical symptoms. Markers sit two to four times above baseline. Nothing hurts. Nothing swells. It runs for years.
That combination is what makes it a public health problem rather than a curiosity. A 2019 review in Nature Medicine placed chronic inflammation among the shared mechanisms behind the leading causes of death worldwide, from cardiovascular disease to type 2 diabetes, fatty liver disease and several cancers.
ACUTE
A sprained ankle or a chest infection. Redness, heat, swelling, pain. It peaks in days and then switches itself off.
LOW-GRADE
No redness, no swelling, no fever. Markers sit two to four times above baseline and stay there for months.
AUTOIMMUNE FLARE
Rheumatoid arthritis or lupus. Swollen joints, morning stiffness beyond an hour, CRP often well past 10 mg/L.
Why your blood test came back normal
Standard CRP was designed to catch infection. It is a good test for that. Most UK laboratories report it as a threshold rather than a value, so a result reads “less than 5 mg/L”, and everything interesting about low-grade inflammation happens under that line. Your report is accurate. It is also blind in exactly the range you care about.
The test that works is high-sensitivity CRP, written hs-CRP. Same protein, finer assay, readable down to fractions of a milligram per litre. It has to be asked for by name.
Here is the part nobody tells British readers. NICE guideline NG238 sets how cardiovascular risk is assessed on the NHS, and recommendation 1.1.7 names QRISK3 as the tool for people aged 25 to 84. QRISK3 asks for age, sex, ethnicity, smoking, blood pressure, cholesterol ratio, BMI, family history and a list of conditions. It asks for no inflammatory marker whatsoever, and the words “C-reactive” appear nowhere in the guideline. So there is no routine NHS pathway that ends with an hs-CRP result in your hand.
That leaves two routes. Ask your GP, who may agree to the sensitive version if your family history warrants it. Or buy it from a UK postal laboratory, singly or inside a longevity panel.
YOUR HIGH-SENSITIVITY CRP, IN MG/L
lower third
middle third
upper third
Reading the number without fooling yourself
The bands come from a 2003 statement by the Centers for Disease Control and Prevention with the American Heart Association, published in Circulation. Below 1 mg/L is the lower third of the population, 1 to 3 mg/L the middle, above 3 mg/L the upper third. Above 10 mg/L, stop interpreting it as background inflammation. Something acute is going on, and the sensible move is to treat the cause and retest in a few weeks.
Four things routinely corrupt a reading, and the first one is breakfast. In a study of 300 hospital patients with coronary heart disease, hs-CRP rose significantly two and four hours after an ordinary meal, and about 32 per cent of those whose fasting value sat at or below 3 mg/L crossed above it after eating. If you eat before the draw you may be handed a number that belongs to your toast.
| What you did | What it does to the reading | What to do instead |
|---|---|---|
| Ate breakfast before the blood draw | Pushes the value up. In 300 heart patients, roughly 32 per cent of those at or below 3 mg/L fasting crossed above it after an ordinary meal | Book a morning slot and go fasted |
| Had a cold, a dental abscess or a flare in the past fortnight | Sends CRP well past 10 mg/L, which is a different question entirely | Wait two to three weeks and repeat |
| Trained hard the day before | A hard session raises inflammatory markers for 24 to 72 hours | Leave three easy days before the test |
| Tested once and drew a conclusion | A single fasting reading is a poor index of what the tissues are doing | Two readings, four to six weeks apart, same lab |
| Switched labs between tests | Assays are not interchangeable, so the trend becomes unreadable | Stay with one provider for the whole series |
The deeper problem is that one measurement is a snapshot of a moving system. The 2015 position paper in the British Journal of Nutrition, led from the University of East Anglia, is blunt about this: the field leans on fasting circulating markers, and those are an insensitive and highly variable index of what the tissues are doing. Two readings, four to six weeks apart, from the same laboratory, tell you far more. The same caution applies to the other way of describing this terrain: oxidative stress runs into an almost identical measurement problem, where the markers on offer describe a moment rather than a state.
What keeps it going
Visceral fat is the biggest single contributor for most people. Fat stored around the organs behaves like a secretory tissue, releasing inflammatory signals into the portal circulation, which is why waist circumference tracks inflammatory markers better than weight does. A slim person with a soft middle can sit in the upper band.
After that the list is unglamorous and long: short or broken sleep, unmanaged stress, smoking, regular alcohol, untreated gum disease, a diet built on ultra-processed food, and hours of uninterrupted sitting. Rarely does one of these do it alone. Usually four or five stack up quietly over a decade.
What it actually feels like
Mostly, nothing. That is the whole difficulty. When people do report something it is vague: tiredness a lie-in does not touch, twenty minutes of stiffness on waking, concentration that slips by mid-afternoon, flat mood, slow recovery, aches with no injury behind them, minor infections that linger. Where those aches spread across whole sheets of tissue rather than settling in one joint, the fascia is usually the tissue involved.
Every one of those has a dozen other explanations, so treat them as a reason to measure, not as a diagnosis. And know the line where this stops being a lifestyle question. Visible joint swelling, morning stiffness lasting more than an hour, fever, night sweats, unexplained weight loss: those need a GP appointment now, not a supplement and a longer walk.
What actually lowers it
Start with the trial that settled the argument in principle. CANTOS enrolled 10,061 patients who had already had a heart attack and whose hs-CRP was 2 mg/L or higher, and gave them canakinumab, an antibody that blocks interleukin-1 beta, or a placebo. The drug did not touch their cholesterol. At the 150 mg dose it still cut the rate of heart attack, stroke and cardiovascular death, with a hazard ratio of 0.85 against placebo over a median 3.7 years of follow-up. Inflammation was not just a marker riding along beside the disease. It was part of the machinery.
patients with a previous heart attack and a high-sensitivity CRP of 2 mg/L or more. Lowering their inflammation, without touching their cholesterol, cut recurrent events.
Ridker et al., CANTOS trial, New England Journal of Medicine, 2017
Read the rest before you get excited. Canakinumab caused more fatal infections than placebo, and all-cause mortality did not improve. It is a hospital drug for a selected population, not something to ask for. What it gives you is confidence that the target is real.
Exercise is where the practical evidence sits, and here the detail matters more than the slogan. A 2022 meta-analysis pooled 24 randomised trials in overweight and obese adults and compared training types head to head. Endurance work beat strength training for lowering CRP, interleukin 6 and visfatin. Combined training beat strength alone for TNF-alpha. Strength training on its own won nothing in this comparison.
| Marker | Which training won | Effect size (SMD) |
|---|---|---|
| C-reactive protein | Endurance over strength | -1.317 (95% CI -2.565 to -0.070) |
| Interleukin 6 | Endurance over strength | -0.363 (95% CI -0.648 to -0.078) |
| Visfatin | Endurance over strength | -0.618 (95% CI -1.015 to -0.222) |
| TNF-alpha | Combined over strength alone | 0.890 (95% CI -0.301 to 1.478) |
| Adiponectin, leptin | No winner | No difference between programmes |
That does not make resistance work pointless, and NICE points clinicians to the UK Chief Medical Officers’ guidelines, which ask for aerobic and muscle-strengthening activity both. But if your target is a CRP number, the aerobic half does most of the lifting.
Then the rest, in rough order of return: losing fat from around the middle, protecting sleep, stopping smoking, cutting alcohol, treating gum disease, and shifting the diet towards oily fish, pulses, vegetables, nuts and olive oil. Single foods rarely move a marker on their own. Diet patterns do, which is also why the food most often blamed turns out to have the weakest case against it: outside coeliac disease, gluten does not survive a blinded trial. Some readers add a bioavailable anti-inflammatory formula alongside those changes, which is reasonable as a supplement to the work and useless as a substitute for it.
How long any of this takes
Longer than a fortnight and shorter than you fear. The marker responds within weeks once weight, activity and sleep start moving, which is why a retest at eight to twelve weeks gives you a usable signal and a retest at two weeks gives you noise. The clinical payoff runs on a much slower clock: CANTOS needed a median of 3.7 years before the difference in events appeared.
Two rules make the follow-up worth doing. Keep the same laboratory, because assays are not interchangeable. And write down what changed between the two draws. Measure, change one thing, measure again is the half of the biohacking habit that survives scrutiny, once the dashboards and the single-night scores are set aside.
Why it matters more after fifty
Inflammatory markers drift upward with age even in people who do everything right. The Italian team who named the phenomenon called it inflammaging, and their 2018 paper in Nature Reviews Endocrinology reframed it as an immune-metabolic process rather than simple immune decline: the ageing body accumulates cellular debris faster than it clears it, and the immune system answers that backlog. That backlog is what the other markers of biological ageing are trying to summarise, which is why telomere length reads as accumulated wear rather than as a clock you can reset.
The practical consequence is that the baseline you are working against rises. A CRP of 2.4 mg/L at 35 and the same value at 65 do not carry the same weight, and the interventions that work do not change with age, they simply matter more. If persistent aches are part of why you started reading this, the same terrain sits underneath a lot of long-running joint and muscle pain, which is why the two questions are worth handling together rather than separately.
Frequently asked questions
What is considered low-grade inflammation?
A high-sensitivity CRP that settles between 1 and 3 mg/L, with no infection and no injury to explain it, is the usual working definition. Above 3 mg/L sits in the upper band. Above 10 mg/L the number has stopped describing background inflammation and is pointing at something acute, so it needs a different conversation with your GP.
What causes low-level inflammation?
Visceral fat is the single biggest contributor in most people, because fat around the organs secretes inflammatory signals of its own. Poor sleep, chronic stress, smoking, alcohol, gum disease, ultra-processed food and long stretches of sitting all add to it, usually four or five at a time.
What does inflammation in the body feel like?
Mostly it does not. When people do notice something it tends to be tiredness that sleep does not repair, twenty minutes of morning stiffness, foggy concentration, low mood and slow recovery after exertion. None of that is specific. Joint swelling, morning stiffness lasting more than an hour, fever, night sweats or unexplained weight loss are different signals and need a GP appointment.
Can I get a high-sensitivity CRP test on the NHS?
Not as a screening test. NICE recommends QRISK3 for estimating ten-year cardiovascular risk, and QRISK3 asks for no inflammatory marker at all, so no routine pathway produces one. Your GP can order a standard CRP when there is a clinical reason. Otherwise it is a private test, sold by UK postal labs.
How long does it take to bring inflammation down?
The marker moves faster than the risk. Retest at eight to twelve weeks, not at two, and expect the first move to come from weight around the middle, sleep and regular aerobic work. The cardiovascular benefit is measured in years: in CANTOS it took a median follow-up of 3.7 years for the difference in events to show.
Can you have low-grade inflammation and still be slim and fit?
Yes. Visceral fat does not always show on the outside, and sleep debt, untreated gum disease, chronic stress and heavy training loads all raise markers in people with a normal BMI. A slim reader with a CRP of 2.8 mg/L is not a measurement error.
Do anti-inflammatory painkillers fix it?
No. Ibuprofen and naproxen work on prostaglandins during a painful episode. They were never designed to change a background inflammatory state, and months of use carry stomach, kidney and cardiovascular risks of their own.
What to take away
Ask for the sensitive test by name, go fasted, and do it twice. Read 1 to 3 mg/L as the middle band and anything past 10 as a different question. Put your effort into waist, sleep and aerobic work, because that is where the measured effects are. And do not expect the NHS to hand you the number unprompted: the guideline governing cardiovascular risk here does not ask for it.
Sources
Furman D., Campisi J., Verdin E. et al. (2019). Chronic inflammation in the etiology of disease across the life span. Nature Medicine, 25(12), 1822-1832. DOI: 10.1038/s41591-019-0675-0
Cifuentes M., Verdejo H.E., Castro P.F. et al. (2025). Low-Grade Chronic Inflammation: a Shared Mechanism for Chronic Diseases. Physiology, 40(1), 4-25. DOI: 10.1152/physiol.00021.2024
Minihane A.M., Vinoy S., Russell W.R. et al. (2015). Low-grade inflammation, diet composition and health: current research evidence and its translation. British Journal of Nutrition, 114(7), 999-1012. DOI: 10.1017/S0007114515002093
Pearson T.A., Mensah G.A., Alexander R.W. et al. (2003). Markers of inflammation and cardiovascular disease: application to clinical and public health practice. Circulation, 107(3), 499-511. DOI: 10.1161/01.cir.0000052939.59093.45
Lin H., Zang J., Fu J. et al. (2022). Non-fasting changes of Hs-CRP level in Chinese patients with coronary heart disease after a daily meal. Scientific Reports, 12(1). DOI: 10.1038/s41598-022-20645-2
Ridker P.M., Everett B.M., Thuren T. et al. (2017). Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease. New England Journal of Medicine, 377(12), 1119-1131. DOI: 10.1056/NEJMoa1707914
Makarewicz A., Jamka M., Geltz J. et al. (2022). Comparison of the Effect of Endurance, Strength, and Endurance-Strength Training on Inflammatory Markers and Adipokines Levels in Overweight and Obese Adults: Systematic Review and Meta-Analysis of Randomised Trials. Healthcare, 10(6), 1098. DOI: 10.3390/healthcare10061098
Franceschi C., Garagnani P., Parini P. et al. (2018). Inflammaging: a new immune-metabolic viewpoint for age-related diseases. Nature Reviews Endocrinology, 14(10), 576-590. DOI: 10.1038/s41574-018-0059-4
