Biomarker reference
Reference guide for 28 biomarkers relevant to peptide research and metabolic health. Normal and optimal ranges with longevity research context.
Biomarker monitoring is a fundamental component of rigorous peptide research. Tracking relevant laboratory values before, during, and after a protocol provides objective data on biological responses, enables early detection of adverse effects, and allows comparison against published clinical trial outcomes.
Different peptide categories affect different biomarker panels. GLP-1/GIP agonists like tirzepatide and retatrutide produce measurable changes in metabolic markers: fasting glucose, HbA1c, insulin, HOMA-IR, lipid panels, and hepatic enzymes. The SURMOUNT and TRIUMPH trials tracked all of these systematically. Growth hormone peptides like CJC-1295 and ipamorelin affect IGF-1 and insulin sensitivity. Healing peptides like BPC-157 may affect hepatic transaminases during tissue repair phases.
This reference distinguishes between two concepts that are often conflated: normal ranges and optimal ranges. Normal ranges (also called reference intervals) are derived from population studies and represent the range containing 95% of a healthy adult population. They reflect what is common, not what is optimal. Optimal ranges are narrower values derived from longevity and performance research β the biomarker levels associated with lowest mortality, best cognitive function, and superior physical performance in observational studies.
For example, the normal fasting glucose range is typically 70-100 mg/dL. The optimal range from longevity research narrows this to 72-90 mg/dL. The distinction matters when interpreting lab results in the context of performance and health optimization research.
This tool covers 28 biomarkers across metabolic, hormonal, inflammatory, hepatic, renal, and cardiovascular domains. For research use only. All results require interpretation by a licensed physician.
| calc.biomarker | calc.unit | calc.normalRange | calc.optimalRange | calc.notes |
|---|---|---|---|---|
IGF-1 Hormonal | ng/mL | 53β220 | 150β250 | GH surrogate marker. Rises with GH peptide use. |
Total testosterone Hormonal | ng/dL | 300β1000 | 600β900 | Males. Optimal for longevity and body composition. |
Free testosterone Hormonal | pg/mL | 8.7β25.1 | 15β25 | Bioavailable fraction. More clinically relevant than total. |
Estradiol (E2) Hormonal | pg/mL | 8β35 | 20β30 | Males. Rises with aromatization of testosterone. |
SHBG Hormonal | nmol/L | 10β57 | 20β40 | High SHBG lowers free testosterone. |
LH Hormonal | mIU/mL | 1.7β8.6 | 3β7 | Luteinizing hormone. Signals testosterone production. |
FSH Hormonal | mIU/mL | 1.5β12.4 | 2β8 | Follicle-stimulating hormone. |
DHEA-S Hormonal | mcg/dL | 70β495 | 200β350 | Declines with age. Longevity marker. |
Cortisol (AM) Hormonal | mcg/dL | 6β23 | 10β18 | Draw fasting, 7β9 AM. |
Fasting glucose Metabolic | mg/dL | 70β99 | 70β85 | Below 85 associated with reduced disease risk. |
HbA1c Metabolic | % | <5.7 | <5.3 | 90-day average blood glucose. |
Fasting insulin Metabolic | mIU/L | <25 | <8 | Key longevity marker. Lower is better in non-diabetics. |
HOMA-IR Metabolic | index | <2.0 | <1.0 | Insulin resistance index = (glucose Γ insulin) / 405. |
Total cholesterol Cardiovascular | mg/dL | <200 | <180 | Context-dependent. LDL particle size matters more. |
LDL cholesterol Cardiovascular | mg/dL | <100 | <70 | Optimal for cardiovascular risk reduction. |
HDL cholesterol Cardiovascular | mg/dL | >40 (M) | >60 | Higher is better. Raises with exercise. |
Triglycerides Cardiovascular | mg/dL | <150 | <100 | Strongly influenced by diet and insulin resistance. |
hs-CRP Cardiovascular | mg/L | <3.0 | <1.0 | Systemic inflammation marker. |
Homocysteine Cardiovascular | ΞΌmol/L | <15 | <9 | Elevated by B12/folate deficiency. Cardiovascular risk. |
ALT Organ function | U/L | 7β56 | 7β35 | Liver enzyme. Rises with hepatotoxic compounds. |
AST Organ function | U/L | 10β40 | 10β30 | Liver + muscle enzyme. |
Creatinine Organ function | mg/dL | 0.74β1.35 | 0.8β1.1 | Kidney filtration proxy. Rises with muscle mass. |
eGFR Organ function | mL/min | >60 | >90 | Estimated glomerular filtration rate. Kidney health. |
Vitamin D (25-OH) Nutrients | ng/mL | 30β100 | 50β80 | Majority of people are deficient. Supplement to 60+. |
Ferritin Nutrients | ng/mL | 30β300 (M) | 50β150 | Iron storage. High ferritin linked to inflammation. |
Vitamin B12 Nutrients | pg/mL | 200β900 | 500β800 | Low end of normal range correlates with neurological symptoms. |
Magnesium Nutrients | mg/dL | 1.7β2.2 | >2.0 | Serum levels are poor indicator; RBC magnesium preferred. |
Zinc Nutrients | mcg/dL | 60β120 | 80β120 | Important for testosterone synthesis and immune function. |
28 calc.of 28 calc.biomarkersShown. Optimal ranges based on longevity and performance research.
toolShell.disclaimer
Frequently asked questions
Which biomarkers should I monitor when using tirzepatide or retatrutide?+
For GLP-1/GIP/glucagon agonists, the key panel includes: fasting glucose, HbA1c, fasting insulin, HOMA-IR (insulin resistance index), complete lipid panel (LDL-C, HDL-C, triglycerides, apolipoprotein B), hepatic enzymes (ALT, AST, GGT), complete metabolic panel, and body weight. For retatrutide specifically, also monitor ketone bodies (beta-hydroxybutyrate) to assess glucagon receptor-mediated fat oxidation, and note any paresthesia symptoms.
What liver enzymes should be monitored with BPC-157 protocols?+
Monitor ALT (alanine aminotransferase) and AST (aspartate aminotransferase) at baseline and periodically during a BPC-157 protocol. BPC-157 has demonstrated cytoprotective effects on the liver in published research, but any novel compound affecting healing pathways warrants hepatic monitoring. Optimal ALT values for men are typically below 30 U/L; for women below 20 U/L β stricter than many laboratory normal ranges.
What does an optimal IGF-1 level look like for growth hormone peptide research?+
IGF-1 (Insulin-like Growth Factor 1) is the primary biomarker for growth hormone activity. Reference ranges are highly age-dependent. For adults in their 30s-50s, a common target in longevity research is the upper quartile of the age-matched normal range β typically 150-250 ng/mL depending on age and sex. Values persistently above the age-matched normal range warrant protocol adjustment.
How often should I test biomarkers during a peptide protocol?+
A standard approach: baseline panel before starting, follow-up at 4-8 weeks, and end-of-protocol panel. For GLP-1 agonists, hepatic enzymes and lipids at 3 months capture the primary metabolic effects. For growth hormone peptides, IGF-1 at 6-8 weeks allows dose adjustment based on response. More frequent testing is warranted if baseline values are borderline or if any adverse symptoms develop.
What is the difference between normal and optimal biomarker ranges?+
Normal ranges (reference intervals) represent the middle 95% of a healthy adult population β they capture what is statistically common. Optimal ranges reflect values associated with best health outcomes in research studying longevity, cardiovascular risk, cognitive function, and physical performance. They are derived from epidemiological studies, not just population statistics. A value can be 'normal' while being suboptimal for health optimization research purposes.
Research background
email.title
email.subtitle