Blood Tests for Longevity: Glycan, IGF-1 and NAD

What blood tests for longevity can and cannot tell you

In our analysis of 2M+ blood test uploads, the patients who benefit most are not the ones chasing a single age score. They are the ones comparing ApoB, HbA1c, creatinine, ALT, ferritin, hs-CRP and vitamin D across 6-24 months, then asking what changed and why.

Kantesti is an AI blood test analyzer that reads longevity panels in clinical context, including routine chemistry, hormones and newer biomarkers such as glycan age, IGF-1 and NAD when they appear on a report. Our clinical standards are described in medical validation, because a longevity result without guardrails can push people toward unnecessary supplements or repeat testing.

Thomas Klein, MD, sees one repeated pattern in reviews: a 46-year-old with a perfect biological age score but an ApoB of 128 mg/dL still needs cardiovascular risk discussion. For a broader evidence-based baseline, our guide to longevity markers explains why standard labs usually come first.

Glycan age test: what the human evidence really shows

IgG N-glycans are sugar structures attached to immunoglobulin G, and their patterns shift with age. Krištić et al. reported in the Journal of Gerontology that glycans can act as biomarkers of chronological and biological age, but that finding does not mean a 7-year glycan gap predicts exactly 7 lost years of life (Krištić et al., 2014).

The practical reading is narrower. A higher glycan age may fit with high hs-CRP above 3 mg/L, central adiposity, insulin resistance, smoking exposure or untreated inflammatory disease; it should not be used alone to diagnose accelerated aging.

We also see sex-hormone context matter. Around menopause, IgG glycosylation can shift in ways that overlap with metabolic and inflammatory changes, which is why patients comparing a glycan age result often benefit from reading it beside our inflammaging biomarker guide rather than treating it as a verdict.

How to read glycan age beside inflammation and metabolism

The hs-CRP cardiovascular risk bands are commonly read as below 1 mg/L for lower risk, 1-3 mg/L for intermediate risk and above 3 mg/L for higher risk when acute infection is excluded. If someone has hs-CRP of 9 mg/L after a respiratory illness, a glycan age result collected the same week is hard to interpret.

A common scenario: a 52-year-old marathon runner receives an older glycan age and panics. If the same panel shows CK of 900 U/L after a race, AST of 89 U/L, normal ALT and normal bilirubin, the biological age score may be contaminated by training stress rather than chronic decline.

For patients who want an inflammation-focused reading, start with whether the result is CRP or hs-CRP, because the assays answer different questions. Our guide to CRP and hs-CRP explains why a mild chronic signal and an acute immune response should not be mixed together.

IGF-1 longevity blood test: why low is not always better

IGF-1 normally declines with age, and adult reference intervals are highly age-dependent. A result of 220 ng/mL may be normal for a 25-year-old but high for some 75-year-olds, depending on the assay and local interval.

Milman et al. reported in Aging Cell that lower IGF-1 was associated with survival in some people with exceptional longevity, especially in specific genetic contexts, but that does not justify pushing IGF-1 below range in everyday patients (Milman et al., 2014). Clinicians worry when low IGF-1 appears with low albumin below 3.5 g/dL, unintentional weight loss or low testosterone.

If IGF-1 is above the age-adjusted upper limit, the question becomes clinical: headaches, jaw or ring-size changes, sweating, sleep apnea and elevated fasting glucose change the risk profile. Our growth hormone testing guide explains why repeat IGF-1 and specialist evaluation can matter more than a single value.

IGF-1 ranges, repeat testing and confounders

Fasting is not always required for IGF-1, but timing and physiology still matter. Severe calorie restriction, uncontrolled diabetes, liver dysfunction and low protein intake can suppress IGF-1 even when growth hormone secretion is not the main problem.

When I review an IGF-1 of 48 ng/mL in a 68-year-old with albumin of 3.1 g/dL and 7 kg weight loss, I do not call that a longevity advantage. The more immediate concern is nutrition, inflammation, liver synthesis or an endocrine axis problem.

Do not compare IGF-1 across labs as if every method is interchangeable. Unit conversions, binding protein effects and assay calibration can make year-to-year results look changed, so read our fasting versus non-fasting guide before over-reading a small shift.

NAD blood test: promising biology, weak clinical cutoffs

NAD is central to redox biology, mitochondrial function and sirtuin-related pathways, but the blood test is technically fragile. Sample temperature, processing delay and whether the lab measures NAD+, NADH, NR, NMN or related metabolites can change the answer.

Martens et al. showed in Nature Communications that nicotinamide riboside supplementation was well tolerated and increased NAD-related metabolites in healthy middle-aged and older adults, but the trial did not prove longer lifespan or fewer heart attacks (Martens et al., 2018). That distinction matters when a patient brings a NAD result of 42 µM and asks whether it means they are aging badly.

Kantesti reads a NAD result as an experimental marker and checks for safer adjacent clues: fasting glucose, HbA1c, ALT, creatinine, B12, folate and medication history. If you are considering supplement pathways, our NAC and glutathione guide shows why redox-related labs need safety context.

NAD precursors: what a blood result cannot prove

The evidence here is honestly mixed. Some human studies show increases in NAD metabolites, while hard outcomes such as mortality, dementia prevention and cardiovascular events remain unproven for NAD precursors.

Lab safety still matters. A patient taking 1000 mg/day of a NAD precursor who also has ALT of 72 U/L, eGFR of 54 mL/min/1.73 m² and new fatigue deserves a medication and supplement review before dose escalation.

Supplements also interact through methylation, liver metabolism and renal clearance. Before stacking products, patients should compare ingredients and timing using a safety-first resource such as our guide on supplement combinations.

Standard labs that often outperform biological age scores

HbA1c of 5.7-6.4% is the usual prediabetes range, and HbA1c of 6.5% or higher on repeat testing supports diabetes diagnosis. That single fact often changes food, medication and follow-up plans more reliably than a biological age score.

ApoB is another underused marker. An ApoB above 130 mg/dL often indicates high atherogenic particle burden, while lower targets such as below 80 mg/dL or below 65 mg/dL may be used for higher-risk patients depending on guideline context.

Kantesti is an AI blood test interpretation platform that prioritizes these actionable markers before ranking experimental longevity tests. For people deciding what to order first, our wellness panel guide separates useful labs from marketing noise.

Why trend analysis beats one biological age number

Most lab reference intervals are population ranges, not personal baselines. A ferritin drop from 80 to 22 ng/mL in a menstruating adult may be clinically relevant months before hemoglobin falls below 12 g/dL.

Kantesti AI interprets trends by comparing prior results, units, timing, sex, age and context rather than treating a flag as the whole story. This is one reason our trend workflow is useful for patients tracking slow lab changes over years.

The practical move is simple: repeat the same marker at the same lab when possible and record major context changes. Weight loss, marathon training, statin initiation, menopause, shift work and infection can all move longevity-relevant markers within 4-12 weeks.

Real-world scenarios that change interpretation

A 39-year-old endurance athlete with AST 88 U/L, CK 1400 U/L and normal bilirubin is not the same as a sedentary patient with AST 88 U/L, ALT 110 U/L and GGT 95 U/L. Exercise timing can explain muscle-related enzyme shifts, as shown in our runner blood test guide.

A 54-year-old in menopause with rising LDL-C, ApoB and HbA1c may see a glycan age shift at the same time. The risk conversation should include body composition, sleep, alcohol, blood pressure and the lipid changes we cover in menopause lab trends.

An 82-year-old with low creatinine, low albumin and low IGF-1 may look metabolically clean because muscle mass is low. In older adults, low creatinine can hide frailty rather than prove excellent kidney health.

Units, reference ranges and why labs disagree

IGF-1 may appear in ng/mL or nmol/L, and conversion depends on molecular assumptions used by the reporting system. NAD metabolites may be reported as µM, nmol/g tissue, relative abundance or a proprietary score.

Routine labs are not immune either. Creatinine can be reported in mg/dL or µmol/L, glucose in mg/dL or mmol/L, and cholesterol in mg/dL or mmol/L; a glucose of 100 mg/dL equals about 5.6 mmol/L.

Before reacting to a trend, check units and lab source. Our guide to different lab units is one of the fastest ways to avoid a false alarm.

How to order a sensible longevity panel

Fasting is useful when triglycerides, fasting glucose, insulin or HOMA-IR are being interpreted. Triglycerides below 150 mg/dL are usually considered normal, while values above 200 mg/dL can distort calculated LDL-C and change cardiovascular interpretation.

If you add glycan age, IGF-1 or NAD, write down sleep, exercise, infection, supplements, alcohol intake and medication changes during the prior 2 weeks. That small note often explains more than another expensive marker.

Patients often ask whether to test everything at once. I usually prefer a staged plan: establish the standard baseline first, fix obvious problems for 8-12 weeks, then decide whether emerging markers add value; our fasting checklist helps avoid preventable pre-test errors.

How Kantesti AI reads longevity panels safely

Kantesti is an AI biomarker interpretation platform used by patients in 127+ countries, and our model is trained to avoid overcalling isolated longevity markers. A high glycan age with normal hs-CRP, normal HbA1c and stable lipids gets a different interpretation than the same glycan result with ApoB 145 mg/dL and ALT 86 U/L.

Our AI reads more than 15,000 biomarker names and unit variants, including scanned PDFs and phone photos, then flags patterns for follow-up in about 60 seconds. The engineering approach behind this workflow is explained in our technology guide.

The validation mindset matters. In a pre-registered benchmark of 100,000 anonymised blood test cases, the Kantesti AI Engine was evaluated across seven medical specialties with hyperdiagnosis trap cases, and the publication is available through the clinical benchmark DOI.

Bottom line: use emerging markers without overclaiming

The safest interpretation order is simple: rule out actionable standard risks first, then ask whether the emerging marker agrees. If HbA1c is 6.1%, ApoB is 132 mg/dL and hs-CRP is 4.2 mg/L, those findings deserve attention regardless of whether a biological age score looks young.

Thomas Klein, MD, and our medical reviewers discourage using any single lab to make supplement, hormone or fasting decisions. Readers who want to understand physician oversight can review Kantesti's medical advisory board and compare recommendations with their own clinician.

Kantesti research publications relevant to this article include: Kantesti Ltd. (2026). Women's Health Guide: Ovulation, Menopause & Hormonal Symptoms. Figshare. https://doi.org/10.6084/m9.figshare.31830721; and Kantesti Ltd. (2026). Clinical Validation of the Kantesti AI Engine (2.78T) on 100,000 Anonymised Blood Test Cases Across 127 Countries. Figshare. https://doi.org/10.6084/m9.figshare.32095435.

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