NAD+ Precursors and Your Labs: Which Biomarkers to Watch

Medical disclaimer: The information in this article is for educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Lab results and reference ranges vary by individual, lab, age, sex, and health history. Always consult a qualified healthcare provider before making any decisions about your health, medications, supplements, or lab testing. LabHealthCharts is a data visualization tool — it organizes and displays your lab data, it does not interpret your results or provide medical guidance.

NAD+ (nicotinamide adenine dinucleotide) declines by roughly 50% between your twenties and fifties in many tissues, and the supplements designed to reverse that decline — primarily NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside) — now rank among the top-selling longevity products worldwide. What most users do not have is a clear picture of which standard blood tests actually reflect what those compounds are doing in the body, and which numbers are worth tracking before, during, and after a supplementation period.

This post covers the biology in plain terms, maps it to specific biomarkers you can order from any major US lab, and explains why a single draw is rarely enough to make sense of what is happening.

What NAD+ actually does and why labs matter

NAD+ is a coenzyme found in every cell. Its primary jobs: shuttling electrons during energy metabolism (in the mitochondria, where ATP is made) and acting as a substrate for a class of proteins called sirtuins and PARPs that regulate DNA repair, inflammation signaling, and gene expression. When NAD+ is abundant, these pathways run efficiently. When it falls, energy production, repair capacity, and metabolic signaling all slow.

NAD+ cannot be measured directly on a standard consumer blood panel — most clinical labs do not offer a validated whole-blood NAD+ assay outside of research settings. That limitation does not make lab tracking useless. It means the relevant question shifts: instead of measuring NAD+ directly, you track the downstream markers that reflect the pathways NAD+ supports. Think of those markers as a functional readout.

A 2023 randomized controlled trial in Nature Aging confirmed that oral NMN supplementation raised blood NAD+ metabolite levels in healthy adults, with measurable effects on muscle insulin sensitivity. That is the kind of mechanistic signal that makes downstream biomarker tracking meaningful.

The metabolic markers: fasting glucose, insulin, and HbA1c

Insulin sensitivity is one of the most studied endpoints in NAD+ precursor trials. NAD+ is required for efficient glucose metabolism in muscle and liver cells. When NAD+ levels fall, mitochondrial function is impaired and cells become less responsive to insulin — a pattern that overlaps significantly with early metabolic dysfunction.

Three tests on a standard metabolic panel capture this axis directly:

Fasting glucose (normal range typically 70–99 mg/dL) reflects how well your cells clear glucose between meals. A value creeping from 90 toward 100 over several visits is a signal worth investigating even before it crosses the prediabetes threshold.

Fasting insulin (typically reported as 2–25 µIU/mL at major labs, though many longevity-focused clinicians prefer values below 10 µIU/mL) is more sensitive to early insulin resistance than glucose alone. You can have a fasting glucose of 95 mg/dL and a fasting insulin of 22 µIU/mL — technically both within reference range, but the combination suggests your pancreas is working harder than it should.

HbA1c (hemoglobin A1c, a measure of average blood glucose over roughly 90 days; normal below 5.7%) tells you how the whole system has been running over the last three months. In the Nature Aging trial referenced above, NMN improved skeletal muscle insulin sensitivity on a clamp test — the kind of effect that should, over months, show up in modest improvements in fasting insulin and HbA1c if the compound is working as intended.

In practice: if you are supplementing NAD+ precursors partly for metabolic reasons, getting a baseline fasting glucose, fasting insulin, and HbA1c before you start and repeating them at three and six months gives you something real to look at.

Lipid panel: triglycerides, HDL, and the metabolic picture

NAD+ metabolism intersects with lipid handling through sirtuins — specifically SIRT1 and SIRT3, which regulate fatty acid oxidation in the liver and mitochondria. When NAD+ is low, fat oxidation slows and triglycerides tend to accumulate. Conversely, interventions that raise NAD+ availability have shown triglyceride-lowering effects in some animal models and early human data.

A 2021 placebo-controlled pilot in Cell Reports Medicine found that NR supplementation in older adults raised whole-blood NAD+ but did not show significant effects on the lipid panel in that small sample. That result matters: it suggests that expecting dramatic lipid shifts from NAD+ precursors alone is probably unrealistic in healthy people, but tracking the markers is still reasonable because the sirtuin pathway touches lipid metabolism in a way that is dose-, context-, and duration-dependent.

What to track: fasting triglycerides (optimal below 100 mg/dL; normal below 150 mg/dL) and HDL cholesterol (typically above 40 mg/dL in men, above 50 mg/dL in women). The triglyceride-to-HDL ratio is a widely discussed proxy for insulin resistance and small dense LDL particle burden. A ratio below 2 is generally considered favorable. These are not NAD+-specific markers — they sit at the intersection of metabolic health broadly — but that is exactly why they belong on a baseline panel.

Liver enzymes: ALT, AST, and GGT

The liver is one of the highest-NAD+ tissues in the body and a primary site of NAD+ synthesis from precursors. ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are the two standard liver injury markers on a comprehensive metabolic panel. Both are typically reported in U/L; major labs use upper limits of normal around 40–55 U/L for ALT and 40 U/L for AST, but these vary by sex and lab method.

Most NAD+ precursor trials have not flagged liver enzyme elevation as a concern at typical supplementation doses. That said, anyone running any supplement over an extended period — especially if combining NAD+ precursors with other compounds, high-dose vitamins, or over-the-counter medications — benefits from a baseline ALT and AST reading and a follow-up check after a few months. A rising ALT trend, even within the normal range, tells a different story than a stable one.

GGT (gamma-glutamyl transferase) deserves a mention here. It is a sensitive liver enzyme that also reflects oxidative stress load independently of overt liver damage. Research published in Atherosclerosis has linked elevated GGT (even within the normal range of 9–48 U/L in men, 9–32 U/L in women at many labs) to cardiovascular event risk. For NAD+ supplementation, GGT is a secondary but worthwhile addition to a baseline panel because it tracks hepatic oxidative burden — one of the targets the NAD+/sirtuin axis is hypothesized to influence.

Inflammation markers: hsCRP and its relationship to NAD+ biology

One of the more compelling mechanistic arguments for NAD+ supplementation is its relationship to inflammaging — the slow, low-grade inflammatory drift that accumulates with age and drives risk for cardiovascular disease, metabolic syndrome, and neurodegeneration. SIRT1 and SIRT2 downregulate NF-κB signaling, which is the master inflammatory pathway. When NAD+ is plentiful, these sirtuins can do their job. When it falls, inflammatory signaling tends to run hotter.

hsCRP (high-sensitivity C-reactive protein) is the most accessible clinical marker for low-grade inflammation. Values below 1.0 mg/L are generally considered low risk; 1.0–3.0 mg/L is intermediate; above 3.0 mg/L is high risk for cardiovascular events per the American Heart Association guidelines. It is not a NAD+-specific marker, but it sits at the center of several pathways NAD+ precursor research targets. If someone starts NMN or NR and their hsCRP drops from 2.8 to 1.4 over six months while also improving sleep and eating better, the chart will show that — and the conversation with their doctor becomes much more specific than 'I think I feel less inflamed.'

Kidney function: creatinine and eGFR

Kidney cells have high mitochondrial density and high NAD+ demand. Preclinical studies have suggested NAD+ depletion plays a role in acute kidney injury and chronic kidney disease progression. A 2023 review in Nature Reviews Nephrology examined NAD+ metabolism in kidney disease and noted that precursor supplementation improved renal outcomes in several animal models. Human trials are limited, but the mechanism is biologically plausible.

For practical lab tracking: serum creatinine and eGFR (estimated glomerular filtration rate — a calculated estimate of how efficiently your kidneys filter waste) are on every comprehensive metabolic panel. eGFR is reported in mL/min/1.73m², with values above 60 considered normal and above 90 considered optimal. These markers are worth including in a baseline panel for anyone over 40 or with any metabolic risk factors, regardless of NAD+ supplementation.

The complete panel to consider before starting NAD+ precursors

*Reference ranges vary by laboratory, age, sex, and method. Always use the range printed on your specific lab report.

A note on holistic interpretation: no marker stands alone

The markers listed above are not NAD+ readouts in isolation — they are windows into metabolic health broadly, and they move together in response to diet, exercise, sleep quality, stress, and aging. Someone supplementing NMN while simultaneously starting resistance training, cutting refined carbohydrates, and improving sleep quality will likely see changes across several of these numbers. The challenge for any individual is knowing which intervention drove which change.

That is why collecting labs before any change is so valuable. A baseline HbA1c of 5.4% at month zero, combined with a fasting insulin of 14 µIU/mL, tells you exactly where you started. If both numbers improve by month six, you have evidence that the intervention period was metabolically productive — even if you cannot attribute the result entirely to one supplement.

For context on how these markers relate to broader longevity risk, the ApoB vs LDL post on this site covers how cardiovascular risk experts think about particle-level markers alongside the standard lipid panel — directly relevant if you are building a longevity-focused baseline panel.

It is also worth noting that NAD+ precursor research remains younger than its commercial popularity suggests. Most robust human RCTs have run for 8–12 weeks with endpoints focused on metabolite levels, insulin sensitivity, or muscle physiology. Longer trials tracking cardiovascular events, cancer incidence, or all-cause mortality do not yet exist at scale. A thoughtful user of this supplement class should hold their biomarker results with appropriate uncertainty — and share the trend data, not just conclusions, with their clinician.

IGF-1 and growth hormone axis markers: relevant if stacking

Some people interested in NAD+ precursors also explore growth hormone secretagogues like GHRP-2 or CJC-1295. When any compound that raises growth hormone activity is in the picture, IGF-1 (insulin-like growth factor 1, measured in ng/mL and highly age-dependent) becomes a relevant monitoring marker. IGF-1 is the primary downstream readout of GH axis stimulation; reference ranges vary substantially with age, and a value that looks normal in a 30-year-old may be elevated for a 55-year-old.

More importantly: NAD+ and the sirtuin pathway interact with IGF-1 signaling in the literature on aging. High IGF-1 is associated with growth and metabolic activity; very low IGF-1 with frailty; and the long-term relationship with longevity is genuinely contested — a detail covered in the Tesamorelin and IGF-1 post on this site. If GH axis compounds are any part of a supplement strategy, IGF-1 belongs on the panel.

Why tracking these markers over time matters more than any single result

A fasting insulin of 13 µIU/mL in January means something very different when viewed alongside a reading of 19 µIU/mL from July of last year than it does as a standalone number. The direction of travel — not the absolute value at a single visit — is usually what informs your understanding of how a supplementation period, a dietary shift, or a period of high stress has affected your metabolic baseline.

This is particularly true for the NAD+ precursor marker set, where the biological effects are gradual and the placebo-adjusted effect sizes in most trials are modest. Expecting a dramatic before-and-after on a single retest is unrealistic. Looking at a six-to-twelve-month chart of fasting insulin, HbA1c, triglycerides, and hsCRP together is a more honest evaluation of what is happening in the body.

LabHealthCharts is built for exactly this kind of longitudinal review. You upload your lab PDFs from Quest, LabCorp, or other major providers — the AI extraction pulls out the values and units automatically — and they populate into charts that show each biomarker as a line across visits rather than a row in a PDF you open once. All 100+ tracked markers live in one account, so you can see fasting glucose moving alongside HbA1c alongside hsCRP in the same view. That kind of visual context is what turns scattered lab results into a readable story over time.

Before your next visit, you can upload your labs and chart your metabolic markers over time — then bring that trend view into the conversation with your clinician rather than a stack of one-off PDFs. LabHealthCharts organizes and visualizes your data; interpretation of what the trend means for your health stays with your care team.

You can also explore the NAD+ precursors page for more on how this compound class fits into the longevity and anti-aging category on the site.

Key Takeaways

NAD+ cannot be measured on a standard consumer panel, but its downstream effects show up in markers you can already order. A practical pre-supplementation panel includes fasting glucose, fasting insulin, HbA1c, a lipid panel (especially triglycerides and HDL), ALT, AST, GGT, hsCRP, and creatinine/eGFR.

The metabolic and liver enzyme markers are the highest-yield targets, because NAD+ precursor research has the strongest human trial data around insulin sensitivity and hepatic NAD+ metabolism. The inflammation markers (hsCRP, GGT) add context around the sirtuin and NF-κB pathways, where the science is mechanistically compelling but human RCT evidence is still maturing.

Concrete next steps to discuss with your clinician:

1. Get a baseline panel before starting — ideally including all nine markers above — so you have a genuine before-and-after comparison rather than guessing at what changed.

2. Retest at three months (glucose, insulin, liver enzymes) and six months (full panel) to capture trend direction rather than noise.

3. Interpret in context: diet, exercise, sleep, and stress all move these markers. Keep notes on what else changed during the period so the lab trends are readable.

4. If combining NAD+ precursors with any GH axis compound, add IGF-1 to the panel and note that age-specific reference ranges apply.

5. A trend chart across six to twelve months is far more informative than a single retest. Track visits over time rather than comparing two isolated PDFs.