Run high-sensitivity C-reactive protein (hs-CRP) first, then repeat it. In the biological-age tests we review here, we most often see a single hs-CRP draw read as a chronic measure. A glycan test earns its place only if you want to track your inflammatory baseline across months.
The two markers get framed as rivals for the same job. They answer different questions, so start by working out which question you are asking.
The Verdict
What hs-CRP Measures
C-reactive protein is made by your liver in response to interleukin-6, a signalling molecule released when tissue is damaged or infected. The high-sensitivity assay reads the low end of the range, roughly 0.1 to 10 mg/L, which is the band that matters for cardiovascular risk rather than for diagnosing an acute infection.
The interpretation bands in wide use are below 1 mg/L for lower risk, 1 to 3 mg/L for average, and above 3 mg/L for higher risk. A result above 10 mg/L is usually treated as an acute event rather than a risk figure, and the standing advice is to retest once the person is well. Our page on hs-CRP covers the bands and the optimal targets in more detail.
Why One hs-CRP Draw Misleads
The half-life of C-reactive protein is around 19 hours, so the number tracks the last day or two rather than the last year. Within-person variation is wide enough that the same healthy person can land in different risk bands on different weeks.
| What moved it | Size of the effect | Whether it is a real inflammation signal |
|---|---|---|
| Any infection, including a cold | Raises it by 10 to 100 times for days | The single most common reason a result reads high |
| Hard exercise in the previous 48 hours | Transient rise from muscle damage | A marathon or an unfamiliar heavy session will show |
| Body fat, particularly visceral | Sustained elevation from adipose interleukin-6 | A genuine chronic signal rather than an artefact |
| Oral estrogen | Roughly doubles it through a first-pass liver effect | Not an inflammatory signal at all, and transdermal estrogen does not do it |
| Poor sleep and acute stress | Modest short-term rise | Enough to move a borderline result across a band |
| Smoking | Sustained elevation | A real signal, and it resolves slowly after quitting |
The oral estrogen row is the one that catches people out. C-reactive protein is synthesised in the liver, and oral estrogen reaches the liver at high concentration before it reaches anywhere else. A study in the Journal of the American College of Cardiology found that eight weeks of oral conjugated estrogens more than doubled C-reactive protein in women whose levels did not move at all on transdermal estradiol. The rise measures hepatic protein synthesis rather than inflammation. Our guide to hormone therapy routes covers where else that first-pass difference shows up.
What IgG Glycans Measure
Immunoglobulin G antibodies carry branched sugar structures, called N-glycans, attached to the stem of the antibody. The composition of those structures determines how strongly the antibody recruits complement and binds immune-cell receptors, which means the same antibody can behave in a more or less inflammatory way depending on its glycan pattern.
The share of antibodies lacking a terminal galactose rises steadily across adult life, and that shift is the basis of glycan-based biological age scoring. Because immunoglobulin G has a half-life of about 21 days and the pattern turns over more slowly than that, a glycan measure reflects the immune environment across roughly the last two to three months. Our page on reading a glycan age result covers what the individual sub-scores mean.
State Markers and Trait Markers
| hs-CRP | IgG glycans | |
|---|---|---|
| What it measures | A liver protein made in response to interleukin-6, rising within hours of any inflammatory trigger | The sugar structures attached to immunoglobulin G antibodies, which shift over months |
| Time window it reflects | The last day or two | The last two to three months |
| Half-life of the thing measured | About 19 hours | About 21 days for the antibody, and the glycan pattern turns over more slowly still |
| Moves with an infection or injury | Yes, by 10 to 100 times | No meaningful short-term movement |
| In a clinical guideline | Yes, a risk-enhancing factor at 2.0 mg/L or above in primary prevention | No |
| Typical cost | Roughly $10 to $30, and included on most standard panels | Roughly $300 to $500, ordered separately |
| Outcome trial behind acting on it | Yes, a statin trial that selected people by this marker | None published |
| Verdict | The first marker to run, and it needs repeating before you read it | A research-grade trait measure, useful for tracking change over months |
The state-and-trait distinction decides which marker to use. A state marker tells you what is happening now, and its usefulness depends on you catching the right moment or repeating it enough times to average out the noise. A trait marker tells you where your baseline sits, and repeating it inside its turnover window measures nothing except assay variation.
Most confusion about these two markers comes from using one as though it were the other. Most people read a single hs-CRP as a settled fact about their chronic inflammation. A smaller group retests glycans after six weeks of a new routine and reads the wobble as progress.
How Glycans Compare with Epigenetic Clocks
Epigenetic clocks read DNA methylation patterns and produce a biological age estimate from them, and they are the more heavily published of the two approaches. Several generations of algorithm exist, each trained differently, and they disagree with each other often enough that which clock you ran matters to the answer you get.
Glycan measures read one system rather than a composite, and that is both the limitation and the appeal. A glycan result carries no information about anything other than immune ageing. In exchange it responds to sustained change: a two-year calorie restriction study published in npj Aging reported movement in glycomic age markers, and glycan patterns shift with hormonal status. Neither approach has a trial showing that acting on the number improves an outcome. Our comparison of methylation clocks against immune age goes through the algorithm differences.
What Each One Predicts
hs-CRP predicts cardiovascular events well enough to sit in a guideline, and that is a higher bar than any glycan measure has cleared. The 2019 primary prevention guideline lists it as a risk-enhancing factor at 2.0 mg/L or above, which means a borderline-risk person with a raised hs-CRP may be moved toward treatment on the strength of it.
Glycan scores have been associated with cardiovascular risk, diabetes, rheumatoid arthritis, and inflammatory bowel disease across observational cohorts. A 2023 cohort study in the journal Engineering built an IgG glycosylation cardiovascular age index and reported that it tracked cardiovascular risk after adjusting for calendar age and C-reactive protein. Association across a cohort is not the same as prediction in an individual, and none of that work has produced a threshold a clinician can act on. That gap is why a glycan result stays outside clinical practice while hs-CRP sits on the standard panel.
IgG Glycan Patterns in Type 2 Diabetes
IgG glycan profiles consistently track type 2 diabetes across multiple independent populations. A Chinese case-control study identified this link using 162 individuals with type 2 diabetes and 162 matched controls from a Beijing health management cohort. Five initial IgG glycans and seven derived traits remained significant after Bonferroni correction and Lasso selection. Researchers validated those markers in the Beijing Xuanwu community cohort of 280 cases and 508 controls. The combined glycan score yielded an odds ratio of 3.78 for type 2 diabetes.
European cohorts demonstrate parallel findings. In the DiaGene study, researchers analyzed 58 IgG glycan traits across 1,886 cases and 854 controls. Replication in the CROATIA-Korcula, CROATIA-Vis, and ORCADES studies, covering 162 cases and 3,162 controls, confirmed five IgG glycans and 13 derived traits in meta-analysis after adjustment for extensive clinical covariates. The investigators described this shared profile as reflecting a pro-inflammatory and biologically-aged state.
Prospective data points the same way. A case-cohort analysis inside the European Prospective Investigation into Cancer and Nutrition (EPIC) Potsdam study drew on a 2,127-person subcohort and 741 incident type 2 diabetes cases. Five IgG glycan peaks, IgG-GP7, IgG-GP8, IgG-GP9, IgG-GP11, and IgG-GP19, remained associated with diabetes risk after multiple testing correction and confounder adjustments, and a composite score based on them tracked higher disease incidence.
These findings remain limited to statistical associations. None of these cohorts tested whether adding a glycan panel to fasting glucose or A1C changes who receives a diagnosis or what clinical steps follow. A diagnosis still rests on fasting glucose and A1C, and our guide to insulin resistance versus prediabetes covers where the line sits.
Repeat-Test Reliability
Glycans win this comparison outright, and that reliability is the strongest argument for the test. The measurement is stable because the underlying biology moves slowly, so two samples taken a fortnight apart from a well person should agree closely. hs-CRP taken the same way frequently does not.
That stability changes how you should schedule each test rather than which is better. hs-CRP needs two or three measurements taken when you are well before a result is worth acting on, and the marginal cost of that is small at $10 to $30 a draw. A glycan measure needs one sample and then six to twelve months of patience before a retest says anything. Testing it more often than that costs several hundred dollars to measure noise.
Who Should Not Buy a Glycan Test
If your question is whether to start a statin, or whether your cardiovascular risk justifies treatment, a glycan test is the wrong purchase and an hs-CRP repeat plus a lipid panel is the right one. Anyone who has not yet run apolipoprotein B (ApoB) and lipoprotein(a) should run those first, since both carry more weight in a risk conversation than either marker here. Our page on ApoB covers why.
A glycan test is also poorly timed for anyone whose hormonal status is changing, including women starting or stopping hormone therapy and anyone beginning testosterone therapy. The measure responds to that change, so the result will reflect it alongside whatever else you were hoping to track. Wait until the hormonal picture is steady.
What would change our answer: a prospective study that measured both markers in the same people and showed glycan scores predicting cardiovascular events beyond what hs-CRP and standard risk factors already capture. If that landed, a glycan test would move from a tracking measure to a risk measure and would belong in the same conversation as hs-CRP. If a head-to-head study instead showed the glycan signal disappearing once body fat and hs-CRP were accounted for, the case for paying several hundred dollars would collapse.
Frequently Asked Questions
Can one hs-CRP result tell me if I have chronic inflammation?
One draw cannot settle it, though a repeated measurement is useful. High-sensitivity C-reactive protein has a half-life of roughly 19 hours and rises 10 to 100 times in response to any acute trigger. A cold, a hard training session, or a recent injury can move a result across two risk bands. Guidelines handle this by asking for more than one measurement, taken at least two weeks apart when the person is well. They also treat a result above 10 mg/L as a sign of acute infection rather than a cardiovascular risk figure. Read that way, it does track chronic inflammation. Read from one draw, it often does not.
What do IgG glycans measure that hs-CRP does not?
IgG glycans measure the inflammatory set point over the past two to three months rather than the state of the immune system on the morning of the blood draw. Immunoglobulin G antibodies carry sugar structures on their stem, and the mix of those structures changes with age. Antibodies lacking a terminal galactose behave in a more pro-inflammatory way, and their share rises steadily across adult life. Because immunoglobulin G has a half-life of about 21 days and the glycan pattern turns over slowly, the measurement is not disturbed by a cold or a hard workout the way hs-CRP is.
Is a glycan age test more accurate than an epigenetic age test?
Neither has been shown to outperform the other in a head-to-head study with hard outcomes, and both are ahead of hs-CRP on stability while behind it on evidence for acting. Epigenetic clocks read DNA methylation and are the more heavily published of the two, with several generations of algorithm. Glycan measures read the immune system specifically, so they capture inflammatory ageing rather than a composite. The practical difference is what they respond to: glycan patterns shift with hormonal status and with sustained lifestyle change over months, which makes them a plausible tracking measure. Neither is in a clinical guideline and neither has a trial showing that acting on the result changes an outcome.
I already ran hs-CRP. Is a glycan test worth several hundred dollars on top?
For a cardiovascular risk decision, no. hs-CRP at 2.0 mg/L or above is the figure the 2019 primary prevention guideline treats as a risk-enhancing factor, and a glycan result adds nothing a clinician can act on within that framework. A glycan test earns its place for a different question: whether a sustained change you are making is moving your inflammatory baseline over months. If that is what you want and you are content to pay several hundred dollars for a research-grade number, it is a reasonable purchase. If you want a risk figure, repeat the hs-CRP instead.
Can a high hs-CRP mean something other than inflammation?
Yes, and oral estrogen is the case most often missed. C-reactive protein is made in the liver, and oral estrogen passes through the liver before reaching the rest of the body. A study in the Journal of the American College of Cardiology found that eight weeks of oral conjugated estrogens more than doubled C-reactive protein in the same women whose levels did not move on transdermal estradiol. The rise reflects hepatic protein synthesis rather than systemic inflammation. Anyone on oral hormone therapy reading an hs-CRP result should know this before treating the number as an inflammation signal.
How often would you repeat each test?
hs-CRP repays a repeat within a few weeks whenever a result is going to drive a decision, because the within-person variation is wide enough that one draw can mislead. Two or three measurements taken when you are well give a far more stable picture than one. A glycan measure works on a different clock. The pattern moves over months, so retesting inside three months mostly measures assay noise rather than change, and six to twelve months is a more sensible interval for tracking.
Will hormone replacement therapy (HRT) change my glycan result?
Yes, and this is one of the better-supported claims for the measure. A randomised trial of 36 premenopausal women, published in 2020, used a hormone-blocking drug to drop gonadal hormones to postmenopausal levels. Participants were then assigned to a transdermal estradiol patch or a placebo. Hormone deprivation raised measured glycan age by a median of 9.1 years, and estradiol prevented the rise almost entirely. The finding cuts both ways. It is good evidence that the measure reflects live biology. It also means a glycan result taken while your hormonal status is changing will capture that change alongside anything else you hoped to track.
Related
- hs-CRP — the bands, the optimal target, and what moves the number
- Glycan age results explained — reading the sub-scores on a glycan report
- Best biological age test — how the test categories compare on evidence and cost
- Methylation clock vs immune age — where the two algorithm families disagree
- ApoB — the marker that carries more weight in a cardiovascular risk conversation
- Normal vs optimal ranges — why reference ranges and target ranges differ
- ESR vs CRP — the other inflammation pair, on a different timescale
The next step for most people reading this is a second hs-CRP draw taken on a week when you are well, which costs little and settles whether the first one meant anything.