Peptides and blood work — what to track
Baseline and end-of-cycle labs for peptide users — CBC, BMP, lipid panel, glucose, HbA1c, IGF-1, liver and kidney markers. What to add, what to skip.
Updated May 7, 2026 · 6 min read
Bloodwork is the cheapest insurance available on a peptide cycle. A baseline panel and an end-of-cycle re-test catches drift signals — insulin sensitivity, lipid changes, kidney or liver stress — before they become symptoms. Most of what you need is one panel, costs under $200 from a direct-to-consumer lab, and doesn't require a prescription. This guide covers what to run, when to run it, and what changes mean.
The baseline-and-recheck framework
The minimum useful pattern:
| Timing | Purpose |
|---|---|
| 1 to 2 weeks before cycle | Baseline — your "normal" while on no peptides |
| End of cycle (last week or first week off) | Detect drift caused by the cycle |
| 4 to 8 weeks after cycle ends | Confirm whether changes reverted or persisted |
A baseline without a recheck is useless. A recheck without a baseline is uninterpretable. Both, every cycle.
Core panel — every cycle
These belong on every cycle regardless of which peptide you are running.
| Lab | What it tracks | Why it matters |
|---|---|---|
| Complete blood count (CBC) | Red and white cells, platelets | Catches inflammation, anemia, contamination response |
| Comprehensive metabolic panel (CMP) | Electrolytes, glucose, kidney, liver | Broad screen of organ function |
| Fasting glucose | Insulin sensitivity snapshot | Drift signal, especially on secretagogues |
| HbA1c | 90-day glucose average | Slower, harder-to-fake glucose marker |
| Lipid panel | Total, LDL, HDL, triglycerides | Cardiovascular drift |
| ALT, AST | Liver enzymes | Liver stress; usually within CMP |
| Creatinine, eGFR, BUN | Kidney function | Clearance status; usually within CMP |
Most direct-to-consumer labs (Quest, LabCorp, the various marketplaces that resell them) bundle CBC, CMP, lipid panel, and HbA1c into one package for roughly $100 to $200 depending on the platform. That is the floor.
Add for GH secretagogues and IGF-1 LR3
If you are running anything that touches the GH or IGF-1 axis, add:
| Lab | What it tracks |
|---|---|
| IGF-1 | Confirms the secretagogue is doing what it should — and how much |
| Fasting insulin | Pairs with glucose for HOMA-IR insulin resistance estimate |
| TSH, free T4 | Thyroid status — GH affects T4 to T3 conversion |
| Free T3 | If long cycle or thyroid history |
Adult IGF-1 reference ranges typically sit between roughly 50 and 250 ng/mL with substantial variation by age and lab — your provider's reference range matters more than a generic number. The useful question is whether your end-of-cycle IGF-1 has moved significantly above your baseline, not whether it sits at a particular absolute number.
Add for longer cycles or stacks
For cycles past 12 weeks or heavy stacks:
| Lab | What it tracks |
|---|---|
| hs-CRP | Systemic inflammation |
| Ferritin | Iron stores; inflammation marker |
| Cortisol (morning) | HPA axis status |
| Total and free testosterone | Gonadal axis |
| Estradiol (sensitive assay if male) | Hormone shift |
| Prolactin | Pituitary status |
These are not every-cycle labs. They earn a spot when the cycle is long, the stack is heavy, or symptoms suggest looking deeper.
What changes mean — orientation, not diagnosis
| Direction | Likely meaning |
|---|---|
| Fasting glucose drift up by 5 to 10 mg/dL | Mild insulin sensitivity reduction; common on secretagogues, watch |
| Fasting glucose above 100 mg/dL on cycle | Stop signal for secretagogues, see when to stop |
| HbA1c drift up by 0.2 to 0.3 | Real signal at this granularity; reassess cycle length |
| HbA1c above 5.7 | Stop the secretagogue cycle |
| ALT or AST above twice upper limit | Investigate; pause cycle |
| Creatinine drift up | Hydration first; if persistent, clinician input |
| LDL drift up by 10 to 20 | Diet and lifestyle confounders likely; recheck |
| IGF-1 elevated above your prior baseline | Expected on secretagogues; very large rises warrant dose reduction |
| WBC elevated post-injection | Possible endotoxin response; check vendor |
Single-lab abnormalities matter less than patterns. One outlier on one panel rarely tells the story; a consistent drift across two cycles does.
What is worth tracking and what isn't
Tracking effort is finite. Labs that earn their spot: glucose, HbA1c, and IGF-1 for anyone running secretagogues; liver and kidney markers for everyone; lipid panel annually rather than every cycle for short users; CBC for catching contamination signals.
Usually wasted spend: comprehensive hormone panels with no symptom basis, heavy-metals testing without exposure history, genetic panels per-cycle, and specialty inflammation panels without a question to answer. A useful test answers a specific question — if you cannot articulate the question, the test is decorative.
Practical lab logistics
| Choice | Notes |
|---|---|
| Direct-to-consumer (Quest, LabCorp via marketplaces) | Cheapest path, no provider needed in most states |
| Through primary care | Insurance covers some, requires reason on chart |
| Specialty / longevity clinics | Most expensive; useful if you want clinician interpretation |
| At-home finger-stick kits | Lower precision; fine for trend-tracking, not for medical decisions |
Fast for 10 to 12 hours before glucose, lipid, and insulin labs. Avoid heavy training the 24 hours before a panel — it shifts CK, AST, and inflammatory markers in ways that aren't about the peptide.
Timing labs around the cycle
A few practical timing notes:
- Baseline at least one week off any peptide; two weeks is better
- End-of-cycle labs in the last week of the cycle if possible — captures peak effect
- For long-acting peptides (CJC-1295 with DAC, MK-677), end-of-cycle reflects sustained exposure
- Reassessment lab 4 to 8 weeks post-cycle confirms whether shifts reverted
- Do not run labs the day of a heavy training session
Tracking over time
A simple spreadsheet with one row per panel and columns for each marker is the useful format. Trends across three or four cycles tell you more than any single panel — if glucose creeps up half a point each cycle, that is a signal even if no individual cycle crossed a threshold.
Bloodwork is the part of peptide use most people skip and most regret skipping later. Run it.