Peptide Bloodwork Guide: Which Blood Tests to Get Before, During and After a Peptide Protocol
A complete guide to peptide blood testing — which markers to request, reference ranges for South African labs, testing schedules, and the warning signs that mean retest now.
Most people starting peptides get their bloods done once — if at all — and never look at them again. That's the single most common mistake in this space, and it's the easiest one to fix.
Bloodwork is not about bureaucracy. It's the only objective way to answer three questions that matter: Is this working? Is it safe? Is something else going on that I'm blaming on the peptide? That last one catches more people than the first two combined. Fatigue on a GLP-1 protocol is far more often low ferritin than it is the peptide itself, and you cannot tell the difference by how you feel.
This guide covers which markers to request, what the numbers mean, when to test, and the symptoms that mean you should stop waiting for your scheduled panel.
Important: This guide is for educational and monitoring purposes only. It does not constitute medical advice. All results must be reviewed by a licensed healthcare practitioner.
How to use this guide
Take the relevant panel section to your pathology lab and request each marker by name. South African labs will not automatically include several of the most useful markers — fasting insulin, magnesium, free T3, hs-CRP and IGF-1 all commonly need to be requested specifically.
Two flags appear throughout:
- Priority marker — test at every phase, not just baseline
- Request specifically — not always included on standard panels automatically
Which bloods do I need? Panels by peptide class
GLP-1 and weight loss peptides
Tirzepatide
GIP / GLP-1 dual agonist — weight loss and metabolic health
A dual hormone agonist that reduces appetite, slows gastric emptying and improves insulin sensitivity. More potent than single GLP-1 agents, which is why pancreatic monitoring is not optional.
Baseline panel
- HbA1c
- Fasting glucose + fasting insulin
- Full lipid panel (LDL, HDL, triglycerides, total cholesterol)
- Full LFTs (ALT, AST, GGT, ALP, bilirubin)
- Lipase + amylase — critical pancreatic baseline
- Creatinine + eGFR + urea
- Ferritin + serum iron + TIBC
- FBC/CBC
- Electrolytes including magnesium
- Vitamin D + B12 + folate
- TSH + free T4
- hs-CRP
- Uric acid
Ongoing monitoring
- HbA1c — every 3 months
- Fasting glucose + insulin — quarterly
- Full lipid panel — quarterly
- ALT + AST + lipase — at 6–8 weeks, then quarterly
- Ferritin — at 6–8 weeks, then quarterly
- eGFR — quarterly
- hs-CRP — quarterly
- Potassium + sodium — if experiencing nausea or vomiting
- B12 — every 6 months
- Uric acid — quarterly
Pancreas alert: If you develop upper abdominal pain radiating to the back, stop tirzepatide immediately and retest lipase and amylase. Lipase above three times the upper limit requires urgent medical review.
Semaglutide
GLP-1 receptor agonist — weight loss and blood sugar control
Suppresses appetite and slows gastric emptying. The same pancreatic cautions apply as with tirzepatide.
Baseline panel
- HbA1c
- Fasting glucose + fasting insulin
- Full lipid panel
- Full LFTs (ALT, AST, GGT, ALP, bilirubin)
- Lipase + amylase — critical baseline
- Creatinine + eGFR + urea
- Ferritin + iron + TIBC
- FBC/CBC
- Electrolytes including magnesium
- Vitamin D + B12 + folate
- TSH + free T4
- hs-CRP
- Uric acid
Ongoing monitoring
- HbA1c — every 3 months
- Fasting glucose — quarterly
- Lipase — at 6–8 weeks, then quarterly
- ALT + AST — quarterly
- Ferritin — quarterly
- Full lipid panel — quarterly
- eGFR — quarterly
- B12 — every 6 months
- Uric acid — quarterly
If you are taking metformin alongside semaglutide, test B12 every 6 months. Metformin significantly depletes B12 stores over time, and the resulting deficiency mimics neurological side effects.
Retatrutide
GIP / GLP-1 / glucagon triple agonist — advanced weight loss
Adds glucagon receptor activity to the dual GIP/GLP-1 mechanism, producing the strongest weight loss effect in the class. It also requires the closest glucose monitoring of any GLP-1 agent.
Baseline panel
- HbA1c
- Fasting glucose + fasting insulin
- Full lipid panel
- Full LFTs (ALT, AST, GGT, ALP, bilirubin)
- Lipase + amylase — critical
- Creatinine + eGFR + urea
- Ferritin + iron + TIBC
- FBC/CBC
- Full electrolytes including magnesium and phosphate
- Vitamin D + B12 + folate
- TSH + free T4 + free T3
- hs-CRP
- Uric acid
Ongoing monitoring
- HbA1c — every 3 months
- Fasting glucose + insulin — quarterly
- Lipase + amylase — at 6–8 weeks, then quarterly
- ALT + AST — quarterly
- Full lipid panel — quarterly
- Ferritin — quarterly
- eGFR + creatinine — quarterly
- Electrolytes — quarterly
- Uric acid — quarterly, and higher risk with rapid fat loss
The added glucagon activity means glucose needs closer monitoring than with single GLP-1 agents. Uric acid matters more here than elsewhere given the speed of fat mobilisation.
Growth hormone secretagogues
Ipamorelin, CJC-1295, GHRP-6 and MK-677
Recovery, muscle, sleep and anti-ageing
These stimulate the pituitary to produce and release growth hormone. Benefits include improved recovery, lean mass, sleep quality and skin. IGF-1 monitoring is non-negotiable — it is the only way to confirm that GH activity is in a safe range, because the dose you take tells you nothing about the response you're getting.
Baseline panel
- IGF-1, age-adjusted — essential
- Fasting glucose + HbA1c — GH raises glucose
- Full LFTs (ALT, AST, GGT)
- Prolactin — GH peptides can elevate it
- Total testosterone + SHBG
- Oestradiol
- TSH + free T4
- FBC/CBC
- Full electrolytes
- Vitamin D + B12
- hs-CRP
Ongoing monitoring
- IGF-1 — at 6–8 weeks, then every cycle
- Fasting glucose — quarterly
- HbA1c — every 3 months
- Prolactin — at 6–8 weeks, then quarterly
- Testosterone + SHBG — quarterly
- ALT + AST — quarterly
- Full lipid panel — every 6 months
If IGF-1 is sustained above 300 ng/mL, reduce dose or frequency immediately. MK-677 in particular raises blood sugar, so HbA1c monitoring matters more with that compound than the others.
Tissue repair peptides
BPC-157, TB-500 and GHK-Cu
Recovery and healing
Potent anti-inflammatory and regenerative compounds. BPC-157 supports gut, tendon and ligament healing. TB-500 promotes cell migration and repair. GHK-Cu stimulates collagen and has antioxidant effects.
Baseline panel
- hs-CRP — the primary anti-inflammatory marker
- Full LFTs (ALT, AST, GGT)
- Creatinine + eGFR
- FBC/CBC
- Full electrolytes
- Vitamin D + B12
- TSH
- Fasting glucose
Ongoing monitoring
- hs-CRP — at 6–8 weeks to track response
- ALT + AST — quarterly
- eGFR — quarterly
- FBC/CBC — quarterly
- Vitamin D + B12 — every 6 months
hs-CRP is the key outcome marker for repair peptides. A measurable drop from baseline at 6–8 weeks is your objective confirmation that anti-inflammatory activity is actually occurring.
Hormonal, nootropic and longevity peptides
PT-141, Epithalon, Selank and Semax
General wellness
A broad category covering sexual health, telomere support, and anxiolytic or cognitive peptides. Requires a general wellness baseline with emphasis on hormonal markers.
Baseline panel
- Total testosterone + SHBG
- Oestradiol
- Prolactin
- TSH + free T4 + free T3
- Full LFTs (ALT, AST, GGT)
- FBC/CBC
- Full electrolytes
- Fasting glucose
- Vitamin D + B12 + folate
- hs-CRP
Ongoing monitoring
- Testosterone + SHBG — every 3–6 months
- Prolactin — quarterly for PT-141 users
- TSH — every 6 months
- ALT + AST — quarterly
- Vitamin D + B12 — every 6 months
- hs-CRP — quarterly
PT-141 elevates prolactin transiently. Check prolactin at baseline and again at 6–8 weeks — elevated prolactin suppresses libido and testosterone, producing the opposite of the intended effect.
Marker reference ranges explained
Reference ranges below are general adult values for South African laboratories. Always interpret against your specific lab's printed reference intervals, as these vary between facilities.
Blood sugar and metabolic markers
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| HbA1c (priority) | Below 5.7%; pre-diabetic 5.7–6.4%; diabetic 6.5% and above | Reflects three-month average glucose. Critical baseline before any GLP-1 protocol. |
| Fasting glucose (priority) | 3.9–5.5 mmol/L | Requires an 8–10 hour fast. GLP-1 peptides lower fasting glucose, so track for hypoglycaemia risk. |
| Fasting insulin (request specifically) | 2.6–24.9 mIU/L; optimal below 10 | Paired with glucose to calculate HOMA-IR. Rarely on standard panels. |
| Uric acid (request specifically) | Men 210–420 µmol/L; women 150–360 µmol/L | Rises with rapid fat mobilisation. Gout risk above 480 µmol/L. |
Calculating insulin resistance: HOMA-IR = (fasting glucose × fasting insulin) ÷ 22.5. A result above 2.0 indicates insulin resistance.
Lipid profile
GLP-1 analogues generally improve lipid profiles alongside weight loss. GH secretagogues can transiently increase LDL.
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| Total cholesterol | Below 5.2 mmol/L | Overall cardiovascular risk. Often improves with GLP-1-driven weight loss. |
| LDL cholesterol (priority) | Optimal below 2.6 mmol/L; acceptable below 3.4 | Primary cardiovascular risk marker. Worth watching on GH peptides. |
| HDL cholesterol | Men above 1.0 mmol/L; women above 1.3 | Protective cholesterol — higher is better. Improves with weight loss and exercise. |
| Triglycerides (priority) | Below 1.7 mmol/L | Drops significantly on GLP-1 protocols. Elevated TG with high glucose raises pancreatic risk. |
Inflammation
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| hs-CRP (priority) | Below 1.0 mg/L low risk; 1.0–3.0 moderate; above 3.0 elevated | The most important inflammation marker. Request the high-sensitivity version specifically. Also a cardiovascular risk predictor. |
Liver function
If ALT or AST rises above three times the upper limit, pause the protocol and retest within two weeks.
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| ALT (priority) | Men 7–56 U/L; women 7–45 U/L | The most sensitive liver injury marker. Elevations above 3× upper limit warrant a protocol pause. |
| AST | 10–40 U/L | Less liver-specific than ALT — also rises after heavy exercise. An ALT:AST ratio above 2 suggests hepatic origin. |
| GGT | Men 8–61 U/L; women 5–36 U/L | Sensitive early-warning marker. Elevated by alcohol, liver disease and some medications. |
| ALP (request specifically) | 44–147 U/L | Elevated in bile duct issues and bone disorders. Usually included on full LFT panels. |
| Bilirubin (total) (request specifically) | 3.4–20.5 µmol/L | Elevated bilirubin combined with raised ALT/AST confirms hepatic stress. |
Kidney function
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| Creatinine | Men 62–115 µmol/L; women 53–97 µmol/L | Affected by muscle mass — athletes run higher baselines. Read alongside eGFR. |
| eGFR (priority) | Above 90 mL/min/1.73m²; mildly reduced 60–89 | The key functional kidney metric. Flag if trending downward across consecutive tests. |
| Urea | 2.5–7.1 mmol/L | Rises with high protein intake and dehydration — common in peptide users, so context matters. |
Electrolytes
GLP-1-related nausea and appetite suppression can deplete key electrolytes. Magnesium is frequently deficient and rarely tested — always request it specifically.
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| Sodium | 136–145 mmol/L | Can drop with nausea, vomiting, or low food and fluid intake. |
| Potassium (priority) | 3.5–5.0 mmol/L | Critical for cardiac rhythm. Can fall with vomiting. Dangerous below 3.0 mmol/L. |
| Magnesium (request specifically) | 0.75–1.0 mmol/L | Frequently depleted, rarely tested. Low magnesium impairs insulin sensitivity and sleep. |
| Calcium | 2.1–2.6 mmol/L | Standard on most panels. Important context for interpreting vitamin D. |
| Phosphate (request specifically) | 0.8–1.5 mmol/L | Falls with aggressive caloric restriction. Part of the refeeding syndrome risk profile. |
Full blood count
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| Haemoglobin (priority) | Men 130–175 g/L; women 120–160 g/L | Anaemia is common on caloric restriction. Appetite suppression can worsen iron-deficiency anaemia. |
| Haematocrit | Men 40–52%; women 37–47% | Rises with dehydration and can mask anaemia. Be well hydrated before testing. |
| White cell count | 4.0–11.0 × 10⁹/L | Elevated indicates infection or inflammation; depressed indicates immune compromise. |
| Platelets | 150–400 × 10⁹/L | Low platelets can indicate clotting issues — relevant for injection-site safety. |
| MCV | 80–100 fL | Low MCV points to iron deficiency; high MCV to B12 or folate deficiency. Always read with haemoglobin and ferritin. |
Iron studies
Iron stores frequently drop during weight loss on GLP-1 protocols. Low ferritin causes fatigue and brain fog that is very often misattributed to the peptide itself.
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| Ferritin (priority) | Men 30–300 ng/mL; women 15–200 ng/mL; optimal above 50 | The most important iron marker. Drops significantly during GLP-1-driven weight loss. |
| Serum iron + TIBC (request specifically) | Iron 9–30 µmol/L; TIBC 45–80 µmol/L | Paired with ferritin to confirm true iron deficiency. Transferrin saturation below 20% is clinically significant. |
Thyroid function
Thyroid dysfunction mimics many peptide side effects — fatigue, weight stall, mood changes. A baseline TSH is essential before attributing any of these to a peptide.
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| TSH (priority) | 0.4–4.5 mIU/L; optimal 1.0–2.5 | Screen first. If abnormal, proceed to free T4 and free T3. |
| Free T4 | 10–23 pmol/L | Run if TSH is abnormal. T4-to-T3 conversion is affected by caloric restriction. |
| Free T3 (request specifically) | 3.1–6.8 pmol/L | The active thyroid hormone. Often suppressed on very low calorie diets even when TSH reads normal. |
Pancreatic markers
GLP-1 analogues carry a class-level warning regarding pancreatitis risk. A baseline lipase is what makes any later result interpretable.
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| Lipase (priority) | 13–60 U/L | More specific than amylase for pancreatitis. Get a baseline before any GLP-1 protocol. Values above 3× upper limit with abdominal pain mean stop and seek urgent review. |
| Amylase | 28–100 U/L | Less specific — also rises with salivary gland issues. Useful alongside lipase as confirmation. |
Vitamins and micronutrients
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| Vitamin D (25-OH) (priority) | 50–125 nmol/L; insufficient 30–50; deficient below 30 | A very common deficiency in South Africa. Affects immunity, mood and insulin sensitivity. |
| Vitamin B12 (priority) | 200–900 pmol/L; optimal above 400 | Depleted by metformin, often co-prescribed with GLP-1s. Deficiency mimics neurological side effects. |
| Folate (request specifically) | Above 7.0 nmol/L | Depletes alongside B12. Required for red cell production — read alongside MCV. |
Hormonal markers
SHBG must always be tested alongside total testosterone. Without it, testosterone values are poorly interpretable, particularly during rapid weight change.
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| Total testosterone | Men 10–35 nmol/L; women 0.5–2.6 nmol/L | Drops with caloric restriction. Weight loss on GLP-1s often improves testosterone in overweight males. |
| SHBG (priority) | Men 16–55 nmol/L; women 17–124 nmol/L | Required to calculate free testosterone. Rises with weight loss — always pair with total testosterone. |
| Oestradiol (E2) | Men 40–161 pmol/L; women varies by cycle | Rises with adipose tissue and drops as weight decreases. Relevant for both sexes. |
| Prolactin (request specifically) | Men 86–324 mIU/L; women 102–496 mIU/L | GH secretagogues can elevate prolactin, suppressing libido and testosterone. Easy to test, often missed. |
Growth hormone axis
Relevant only for users of ipamorelin, CJC-1295, GHRP-2, GHRP-6, MK-677 and hexarelin. IGF-1 reflects actual GH effect, not peptide dose.
| Marker | Reference range (SI) | What it tells you |
|---|---|---|
| IGF-1 (priority) | Age-adjusted, approximately 115–300 ng/mL — your lab provides the age-specific range | The primary marker for verifying and monitoring GH peptide effect. Test before starting, at 6–8 weeks, then quarterly. |
IGF-1 above 300 ng/mL sustained: reduce secretagogue dose or frequency immediately. Do not continue escalating without IGF-1 confirmation. Chronically elevated IGF-1 is associated with adverse long-term outcomes.
Testing schedule: when to get bloods
Four phases structure the monitoring protocol. Baseline is mandatory before any peptide is started, and the 6–8 week check is the most critical safety window — it is the one people skip and the one that catches problems early.
| Marker / panel | Baseline | 6–8 weeks | Quarterly | Annual |
|---|---|---|---|---|
| HbA1c | ✓ | ✓ | ✓ | ✓ |
| Fasting glucose + insulin | ✓ | ✓ | ✓ | ✓ |
| Full lipid panel | ✓ | — | ✓ | ✓ |
| hs-CRP | ✓ | ✓ | ✓ | ✓ |
| Full LFTs (ALT, AST, GGT, ALP, bilirubin) | ✓ | ✓ | ✓ | ✓ |
| Creatinine + eGFR + urea | ✓ | ✓ | ✓ | ✓ |
| Full electrolytes including magnesium | ✓ | — | ✓ | ✓ |
| FBC/CBC | ✓ | — | ✓ | ✓ |
| Ferritin + iron + TIBC | ✓ | ✓ | ✓ | ✓ |
| TSH + free T4 + free T3 | ✓ | — | ✓ | ✓ |
| Lipase + amylase | ✓ | ✓ | — | ✓ |
| Vitamin D + B12 + folate | ✓ | — | — | ✓ |
| Testosterone + SHBG + oestradiol | ✓ | — | ✓ | ✓ |
| Prolactin | ✓ | ✓ | ✓ | ✓ |
| Uric acid | ✓ | — | ✓ | ✓ |
| IGF-1 (GH peptide users only) | ✓ | ✓ | ✓ | ✓ |
Trend matters more than any single value. A marker moving consistently in one direction across two or more quarters — even while staying inside the reference range — should be flagged and discussed with your healthcare practitioner. A single reading tells you where you are; a series tells you where you're going.
Immediate retest triggers
Do not wait for your scheduled panel if any of the following occur.
Liver concern
Symptoms: Nausea, jaundice (yellowing of eyes or skin), right upper quadrant pain, or unexplained fatigue.
Action: Retest ALT, AST, GGT and bilirubin within two weeks. If results exceed three times the upper limit, pause peptide use immediately and consult a doctor.
Pancreas concern
Symptoms: Epigastric pain radiating to the back, persistent vomiting, or severe abdominal cramping.
Action: Retest lipase and amylase immediately. Pause all GLP-1 use. Seek urgent medical review if lipase exceeds three times the upper limit.
Kidney concern
Symptoms: Oedema (swelling in legs or face), reduced urine output, dark or foamy urine.
Action: Retest creatinine, eGFR, urea and full electrolytes. Do not resume the protocol until levels are stable.
Hypoglycaemia
Symptoms: Shakiness, sweating, confusion or palpitations — particularly on GLP-1 protocols.
Action: Retest fasting glucose and insulin. Review your dosing protocol with a practitioner before continuing.
Signs of GH excess
Symptoms: Joint pain, water retention, tingling or numbness in extremities, or carpal tunnel symptoms on secretagogue protocols.
Action: Retest IGF-1 immediately. If above 300 ng/mL, reduce or halt secretagogue use and consult your practitioner.
Unexplained fatigue
Symptoms: Persistent fatigue, brain fog or poor recovery not explained by training load or sleep.
Action: Rule out low ferritin, low vitamin D, low B12 and thyroid dysfunction (TSH and free T3) before attributing it to the peptide. This is the single most common misattribution in peptide use.
Frequently asked questions
Do I really need bloodwork before starting peptides?
Baseline bloodwork is what makes every subsequent test interpretable. Without it, a lipase reading of 55 U/L at week eight is meaningless — you have no idea whether that's your normal or a doubling. Baseline is the reference point that turns later numbers into information.
How much does a peptide blood panel cost in South Africa?
Cost varies considerably between pathology providers and depends on how many markers you request. Requesting a targeted panel based on your specific peptide, rather than a broad screen, keeps costs down significantly. Discuss the marker list with your practitioner, who can advise on which are essential for your protocol versus useful additions.
Can I get these tests without a doctor's referral?
Requirements vary between pathology providers in South Africa. Many tests require a practitioner referral form. Your practitioner can issue a request form listing the specific markers from this guide.
Which single marker matters most?
It depends on your compound. For GLP-1 users, lipase — because a baseline is what allows any later abdominal symptom to be properly assessed. For GH secretagogue users, IGF-1, without question, because it is the only marker that reflects your actual GH response rather than your dose. For repair peptides, hs-CRP, because it tells you whether the compound is doing anything at all.
My results are all "in range" but I feel terrible. What now?
In-range is not the same as optimal, and it is not the same as unchanged. Compare against your baseline rather than the reference interval — a ferritin that has fallen from 90 to 35 ng/mL is still technically in range for many labs, but that drop is very likely to be why you feel tired. This is exactly why the trend matters more than the value.
How long after starting should I retest?
Six to eight weeks. This is the most critical safety window and the one most commonly skipped. It catches liver enzyme rises, pancreatic changes, ferritin depletion and IGF-1 overshoot while they are still easy to correct.
Bring your results to us
If you're running a Striata protocol and want help interpreting a set of results, get in touch. We'll walk through the numbers with you and flag anything worth discussing with your practitioner.
Website: striatalabs.co.za
Email: info@striatalabs.co.za
WhatsApp: +27 78 213 7905
This document is produced by Striata Research Peptides for educational and client monitoring purposes only. It does not constitute medical advice. All protocols must be supervised by a licensed healthcare practitioner. Striata accepts no liability for actions taken based solely on the content of this guide.
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