GLP-1 Monitoring: Bloodwork, Tests & What to Track
Good GLP-1 care isn't just the prescription—it's monitoring to ensure it's working and safe. This guide explains what bloodwork you need, when, and where to get it in the UK.
Baseline Testing (Before Starting GLP-1)
Get these tests before your first injection to establish a baseline:
| Test | Why | Normal Range | |------|-----|--------------| | HbA1c | Glucose control (3-month average) | <5.7% ideal | | Fasting glucose | Blood sugar baseline | <5.6 mmol/L ideal | | Total cholesterol | Cardiovascular health | <5.2 mmol/L ideal | | LDL cholesterol | "Bad" cholesterol | <2.6 mmol/L ideal | | HDL cholesterol | "Good" cholesterol | >1.0 mmol/L ideal | | Triglycerides | Fat in blood | <1.7 mmol/L ideal | | Kidney function (eGFR) | Kidney health | >60 mL/min/1.73m² OK | | Creatinine | Kidney marker | 60–110 μmol/L typical | | Liver function (ALT, AST) | Liver health | <40 IU/L ideal | | Albumin | Protein, nutrition | 35–50 g/L | | Thyroid (TSH) | Thyroid function | 0.4–4.0 mIU/L | | Calcitonin | MTC screening (optional) | <10 pg/mL | | Vitamin B12 | Baseline before absorption changes | >200 pg/mL | | Iron/ferritin | Baseline iron stores | Ferritin >20 ng/mL |
Follow-Up Testing: Timeline & Schedule
3 Months (First Check-In)
Purpose: Assess early response, check safety markers
Tests:
- Fasting glucose
- HbA1c (if diabetic, or if high baseline)
- Weight & BMI
- Blood pressure
Why: Verify weight loss trajectory, ensure glucose control (if diabetic), ensure no adverse effects
6 Months (Mid-Course Assessment)
Purpose: Assess sustained progress, full metabolic panel
Tests:
- HbA1c
- Total cholesterol, LDL, HDL, triglycerides
- Kidney function (eGFR, creatinine)
- Liver function (ALT, AST, bilirubin)
- TSH
- Vitamin B12
- Weight, blood pressure
Why: Verify metabolism improving, kidney/liver safe, B12 declining (start supplementing if not already)
12 Months (Annual Assessment)
Purpose: Full reassessment before renewal
Tests:
- Full metabolic panel (as above)
- Iron/ferritin (assess hair loss risk factors)
- Weight, body composition if possible
- Blood pressure
Why: Comprehensive health picture, assess need for continued treatment
Testing Options in the UK
Option 1: Private GP / Clinic Bloodwork
Who: Your private GLP-1 clinic or private GP
Cost: Usually included in clinic cost, or £30–100 per panel
Pros:
- Integrated with your care
- Doctor reviews results
- Quick turnaround
Cons:
- More expensive than standalone testing
- Sometimes bundled (can't cherry-pick tests)
Option 2: Medichecks (Online, Home Blood Test)
Website: medichecks.com
How it works:
- Order test online
- Finger-prick blood test kit arrives
- You do test at home, post sample back
- Results in 2–3 days
- Report + interpretation online
Cost: £40–150 per panel (depending on test)
Popular panels for GLP-1 users:
- "Full Blood Count + Metabolic Screening": ~£99
- "Lipid Panel": ~£30
- "Thyroid Function": ~£35
- "Iron Panel": ~£40
- Custom panel: build your own
Pros:
- Affordable
- Convenient (home testing)
- Can order anytime
- Good interpretation
Cons:
- Results come electronically; need to interpret yourself (or email your prescriber)
- Finger-prick sometimes tricky
- 2–3 day wait
Option 3: NHS GP Bloodwork
Who: Your NHS GP
Cost: Free
How it works:
- Request appointment with GP
- Discuss GLP-1 monitoring needs
- GP orders bloodwork
- You attend local phlebotomy clinic
- Results back in 1–2 weeks
Pros:
- Free
- Integrated with NHS records
- GP reviews + advises
Cons:
- Long waits for appointments
- Limited test options (NHS usually covers basics only)
- GPS may be unfamiliar with GLP-1 monitoring
Note: Some NHS GPs will monitor GLP-1 users if you request; others won't (depends on practice).
Option 4: Private Phlebotomy Clinics
Examples: London Andrology Clinic, Nuffield Health, Spire
Cost: £100–200+ per test
Pros:
- Quick turnaround
- Arm blood draw (easier than finger prick)
- Good quality lab work
Cons:
- More expensive
- Need to visit clinic in person
- Still need to interpret or send to your doctor
Key Tests Explained: What to Look For
HbA1c (Most Important If Diabetic)
What it measures: 3-month average blood glucose
Why it matters: Shows if GLP-1 is controlling blood sugar
Target on GLP-1:
- Diabetic: <7% (some prefer <6.5%)
- Non-diabetic: <5.7% (this is "prediabetes reversal" territory)
What improves it: GLP-1 itself (directly lowers glucose) + weight loss (improves insulin sensitivity)
Lipid Panel (Total, LDL, HDL, Triglycerides)
What it measures: Cholesterol and fats in blood
Why it matters: Cardiovascular health (weight loss typically improves lipids)
Targets on GLP-1:
- Total cholesterol: <5.2 mmol/L
- LDL: <2.6 mmol/L
- HDL: >1.0 mmol/L
- Triglycerides: <1.7 mmol/L
What improves it: Weight loss (especially visceral fat loss), improved insulin sensitivity
Kidney Function (eGFR, Creatinine)
What it measures: How well kidneys filter waste
Why it matters: GLP-1 (particularly semaglutide) can slightly reduce kidney function; monitor for safety
Targets:
- eGFR: >60 mL/min/1.73m² (OK)
- eGFR 45–59: caution; monitor more frequently
- eGFR <45: discuss with prescriber (may need dose adjustment)
- Creatinine: should stay stable
Reality: Most people's kidney function stays same or improves (weight loss helps). Declines are rare and usually small.
Liver Function (ALT, AST, Bilirubin)
What it measures: Liver health
Why it matters: Rarely affected by GLP-1, but baseline check is prudent
Targets:
- ALT: <40 IU/L
- AST: <40 IU/L
- Bilirubin: <20 μmol/L
What happens: Usually improves (weight loss reduces fatty liver)
Vitamin B12
What it measures: B12 level in blood
Why it matters: GLP-1 reduces B12 absorption (slow stomach emptying); deficiency causes fatigue, neuropathy, hair loss
Targets:
-
400 pg/mL: normal, no action needed
- 300–400 pg/mL: low-normal, consider supplementing
- <300 pg/mL: deficiency, supplement or injectable
What happens: Often declines 3–6 months in; oral B12 supplementation prevents deficiency
Action: Start oral B12 supplementation (1000–2000 mcg daily) prophylactically.
Iron / Ferritin
What it measures: Iron stores
Why it matters: Low iron worsens hair loss on GLP-1; rapid weight loss depletes iron
Targets:
- Ferritin: >30 ng/mL (below this increases hair loss risk)
- Serum iron: 12–25 μmol/L
What happens: Often declines with rapid weight loss; supplementation helps
Action: Check at baseline + 6 months; supplement if ferritin <30
When to Escalate Monitoring
More frequent testing if:
- Kidney function declining (eGFR dropping)
- Liver enzymes rising (ALT/AST elevated)
- Diabetic with poor glucose control (HbA1c not improving)
- Signs of B12 deficiency (fatigue, neuropathy symptoms)
Escalate to: Check every 3 months instead of 6 months; discuss with prescriber about need to modify GLP-1 or increase monitoring
Red Flags: When to Contact Prescriber Immediately
Results requiring urgent discussion:
- eGFR <45 (kidney function compromised)
- ALT/AST >100 (liver dysfunction)
- HbA1c rising despite GLP-1 (not responding)
- Calcitonin elevated (thyroid concern, though rare)
Realistic Cost for Full Year of Monitoring
Option 1: Private clinic included
- Cost: Usually £180–250/month (Juniper, Oviva, etc.)
- Monitoring: Included in subscription
Option 2: Budget private (Numan, Manual) + Medichecks
- Clinic: £150–180/month
- Medichecks baseline: £99
- Medichecks 3-month: £99
- Medichecks 6-month: £99
- Medichecks 12-month: £99
- Total first year: ~£2100–2400
Option 3: NHS GP + Medichecks
- NHS GP: Free (but hard to access, limited monitoring)
- Medichecks (1-2 panels/year): ~£100–200
- Total: ~£100–200/year
Key Takeaway
Minimum monitoring: Baseline tests before starting, then annually (HbA1c, lipids, kidney function, B12)
Ideal monitoring: Baseline + 3-month + 6-month + 12-month panels, with B12 supplementation started prophylactically
Most cost-effective: Use Medichecks for follow-up testing; have private prescriber or NHS GP interpret
Next Steps
- GLP-1 side effects & safety guide
- B12 & supplements on GLP-1
- Thyroid & GLP-1 safety
- Private clinic comparison
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Disclaimer: This is educational information. Consult your prescriber for specific monitoring recommendations based on your health profile.