hsCRP: The Inflammation Marker Worth Tracking

What It Measures and Why It Predicts

C-reactive protein is produced by hepatocytes in response to interleukin-6, which is released by immune cells, by senescent cells as part of their secretory phenotype, and by adipose tissue. It functions in immune defence by binding damaged cell membranes and promoting clearance.

Its value as a marker comes from its position: it integrates interleukin-6 signalling from many sources into a single stable, inexpensive and widely available measurement. It is a downstream summary of inflammatory activity rather than an inflammatory driver, and that distinction is the key to interpreting it correctly.

Cohort evidence for its predictive value is extensive. Elevated high-sensitivity C-reactive protein associates with cardiovascular events, all-cause mortality, incident type 2 diabetes, cognitive decline and frailty, generally with a graded relationship rather than a threshold effect. A landmark trial in people with elevated high-sensitivity C-reactive protein but unremarkable LDL cholesterol found that statin therapy reduced cardiovascular events in that group, which established the marker's clinical usefulness for identifying people who benefit from intervention.

Marker Versus Mechanism

This distinction deserves its own section because it is routinely lost.

Mendelian randomisation studies, which use genetic variants as natural experiments, have examined variants that raise or lower circulating C-reactive protein directly. Those variants do not produce corresponding differences in cardiovascular outcomes. Meanwhile, variants affecting interleukin-6 signalling upstream do associate with outcomes, and trials targeting interleukin-1 beta and interleukin-6 pathways have reduced cardiovascular events.

The conclusion is clear: C-reactive protein reports inflammation, and inflammation matters, but the protein itself is not the harmful agent. Practically, this means an intervention that lowers the number without lowering the underlying inflammatory activity has achieved nothing, and an intervention that lowers underlying inflammation will generally lower the number as a side effect. Read it as a gauge, not as a target.

Measuring It Properly

More measurement errors are made with this marker than with almost any other in routine use, and they are all avoidable.

• Not within two weeks of any infection. A cold, a dental procedure or a gastrointestinal upset can raise it many-fold. A value taken in that window is measuring the event, not the baseline.
• Not within forty-eight to seventy-two hours of hard exercise. Intense or unaccustomed training, particularly eccentric loading, raises it substantially. Endurance events raise it for days.
• Not after injury or surgery. Wound healing is an inflammatory process.
• Repeat before interpreting. Biological variability is high. A single value should be confirmed at least two weeks later before it informs a decision, and two concordant values are worth far more than one.
• Note the medications and hormones. Oestrogen-containing contraceptives and oral hormone therapy raise it. Statins lower it independently of lipid effects. Non-steroidal anti-inflammatory drugs and corticosteroids lower it.
• Use the high-sensitivity assay. Standard C-reactive protein assays lack resolution at the low concentrations that matter here.

Seasonal variation is also real, with higher values common in winter in many populations, which argues for season-matched comparison when tracking year on year.

What Raises It Chronically

Ranked roughly by how often each explains an elevated value in an otherwise well person.

1. Visceral adiposity. The most common single explanation. Adipose tissue produces interleukin-6 directly, and the relationship with waist circumference is strong.
2. Smoking. Continuous inflammatory stimulus.
3. Periodontal inflammation. Common, silent and specifically addressable. Frequently the explanation in a lean, fit person with a stubbornly elevated value.
4. Sleep insufficiency and sleep-disordered breathing. Both raise it measurably.
5. Insulin resistance. Bidirectionally linked.
6. Oestrogen-containing medication. Raises it without indicating a problem, which is a common cause of confusion.
7. Chronic infections and autoimmune conditions. Clinical rather than optimisation territory.
8. Chronic psychosocial stress. Associated through neuroendocrine and behavioural routes.
9. Alcohol. Dose-related above moderate intake.

A persistently elevated value with none of these present is a reason for clinical assessment rather than for supplementation, because the differential includes things that matter.

What Lowers It

In rough order of effect size, and noting that the objective is lower inflammation rather than a lower number.

• Visceral fat reduction. Reductions with meaningful weight loss are substantial and consistent.
• Smoking cessation.
• Regular exercise. Lowers resting values despite raising them acutely per session.
• Addressing periodontal inflammation. Specific, cheap and evidence-supported.
• Sleep restoration.
• Dietary pattern. Higher fibre, legumes, vegetables, fish and unsaturated fats; lower ultra-processed intake.
• Omega-3 at above 2 grams per day of combined EPA and DHA. Meta-analyses report reductions, largest where baseline is elevated.
• Curcumin with an absorption enhancer, and other polyphenols. Modest effects in human trials.
• Statin therapy, where clinically indicated. Lowers it independently of lipid effects, which is a clinical decision rather than an optimisation one.

Building a Sensible Tracking Routine

A workable structure: measure twice at baseline, two to four weeks apart, under standardised conditions, and take the pair rather than either value alone. Address the highest-ranked applicable contributors for twelve weeks. Re-measure under the same conditions and in the same season where possible.

Pair it with the neutrophil-to-lymphocyte ratio, which comes free with any full blood count and adds independent information, and with ferritin, remembering that high ferritin with normal iron indices usually reflects inflammation rather than iron stores.

The temporal caution worth repeating: this marker is state-sensitive by design. Its responsiveness is what makes it useful for tracking and what makes single readings unreliable. A member who measures it after a marathon and again after a quiet fortnight has learned about their calendar, not their biology.