GLP-1 / Ozempic / Wegovy Blood Tests UK (2026): What to Monitor and When
Important — monitoring is part of clinical care, not a substitute for it
GLP-1 drugs (semaglutide, tirzepatide) are powerful prescription medicines. If you are prescribed one, your monitoring should be arranged by your prescriber — the doctor or clinic responsible for your treatment. This guide explains what monitoring typically involves and why, so you can have an informed conversation and check that your monitoring is actually being done. It is information, not medical advice, and a private blood panel is a supplement to — never a replacement for — prescriber-led care. If you obtained a GLP-1 drug without proper prescriber oversight, that monitoring gap is itself a safety risk. Full disclaimer.
GLP-1 receptor agonists — semaglutide (sold as Ozempic for type 2 diabetes and Wegovy for weight management) and tirzepatide (Mounjaro, a dual GIP/GLP-1 agonist) — are now among the most widely prescribed drugs in the UK. They are available through NHS specialist obesity services and, increasingly, through private online clinics (Numan, Superdrug Online Doctor, Boots, independent GPs and pharmacies). With millions of UK users, a practical question follows: what should you have checked, and when? This guide lays out the baseline, 3-month and 6–12-month monitoring panels, explains why each marker matters, and is honest about where private testing helps and where it does not.
The 90-second answer
If you only read one box
- Get a baseline panel before starting: HbA1c + glucose, lipids, kidney function, liver function, amylase/lipase, thyroid (TSH/fT4), FBC, and nutritional markers (ferritin, B12, folate, vitamin D). Plus blood pressure.
- At ~3 months: HbA1c, lipids, kidney function, liver function, plus weight and waist. Nutritional markers as an early flag.
- At 6–12 months: repeat the full metabolic panel; thyroid if neck symptoms or family history of medullary thyroid cancer.
- Monitoring is the prescriber's job. NHS obesity-service prescriptions include it; if you use a private clinic, confirm explicitly that they arrange monitoring bloods.
- Red flags = test now, don't wait: severe abdominal pain (pancreatitis → amylase/lipase), persistent vomiting + weakness (dehydration → kidney function + electrolytes), neck lump + voice change (→ thyroid).
- Private monitoring options: Medichecks weight-management / metabolic panels (~£49–£149) or Bluecrest metabolic panels — to supplement, not replace, prescriber monitoring.
Why monitoring matters (it's not just "is it working?")
The obvious reason to test is to confirm the drug is improving your metabolic numbers. But monitoring on a GLP-1 drug is also about safety. These drugs touch several organ systems:
- Thyroid — GLP-1 drugs carry a regulatory warning about a possible medullary thyroid carcinoma (MTC) risk, based on rodent studies; they are contraindicated with a personal/family history of MTC or MEN 2.
- Pancreas — a recognised (uncommon) risk of pancreatitis; amylase/lipase baseline helps, and severe abdominal pain needs prompt testing.
- Kidneys — GI side effects (vomiting, diarrhoea) can cause dehydration and a temporary drop in kidney function.
- Glucose & HbA1c — HbA1c falls, sometimes fast; combined with insulin or sulfonylureas this raises hypoglycaemia risk and may require dose changes.
- Liver — often improves with weight loss (fatty liver), but worth tracking.
- Gallbladder — rapid weight loss increases gallstone risk; investigated by ultrasound, not blood test.
- Nutrition — sharply reduced food intake can unmask deficiencies in iron, B12, folate and vitamin D.
Before starting: the baseline panel
A baseline gives you the "before" picture against which all later results are compared. A sensible pre-treatment panel:
| Test | Why at baseline |
|---|---|
| HbA1c + fasting glucose | Glycaemic starting point; defines diabetes/prediabetes status |
| Lipid profile (total chol, LDL, HDL, triglycerides) | Cardiometabolic baseline; usually improves on treatment |
| Kidney function (eGFR, creatinine, urea) | Reference point before any dehydration risk from GI effects |
| Liver function (ALT, AST, GGT, ALP, bilirubin) | Baseline hepatic status; fatty liver common in this group |
| Amylase / lipase | Pancreatic baseline before any pancreatitis concern |
| Thyroid (TSH + free T4) | Baseline; MTC-risk context and to exclude thyroid disease |
| Ferritin, B12, folate, vitamin D | Nutritional baseline before caloric restriction |
| Full blood count (FBC) | General baseline; anaemia screen |
| Blood pressure (not a blood test) | Part of cardiometabolic baseline; often improves with weight loss |
If you are prescribed via an NHS specialist obesity service, this baseline is part of the programme. If you are using a private clinic, ask directly: "Do you arrange baseline and follow-up monitoring bloods, or do I need to?" Do not assume — responsibility for monitoring sits with the prescriber, and some online clinics do less than others.
At 3 months
Three months is the first meaningful checkpoint — long enough for HbA1c (which reflects ~3 months of average glucose) to show change, and for early lipid and weight improvements:
- HbA1c — confirms glycaemic improvement; flags hypoglycaemia risk if on concurrent glucose-lowering drugs.
- Lipid profile — rapid improvement is often visible by now.
- Kidney function (eGFR/creatinine) — checks no dehydration-related decline.
- Liver function tests — tracks hepatic effect; fatty-liver markers often improve.
- Weight + waist circumference — the headline efficacy measures.
- Ferritin / B12 / vitamin D — early nutritional flag as intake drops.
At 6–12 months
- Full metabolic panel — repeat HbA1c, lipids, kidney and liver function.
- Nutritional markers — ferritin, B12, folate, vitamin D, especially after substantial weight loss.
- Thyroid — only if neck symptoms develop or there is a family history of MTC; not routine for everyone.
- Gallbladder — symptoms (severe right-upper-abdominal pain after meals) → ultrasound, not a blood test.
- Bone health — a consideration for long-term use with very large weight loss; discuss with your prescriber.
Red-flag symptoms — test immediately, don't wait for a review
| Symptom | Concern | Action |
|---|---|---|
| Severe, persistent upper abdominal pain (may radiate to back) | Pancreatitis | Urgent assessment + amylase/lipase |
| Persistent vomiting/diarrhoea with weakness or dizziness | Dehydration / acute kidney injury | Kidney function + electrolytes; rehydrate |
| New neck lump, persistent hoarseness, difficulty swallowing | Thyroid (MTC context) | Thyroid evaluation |
| Severe right-upper-abdominal pain after fatty meals | Gallstones | Ultrasound (not a blood test) |
| Shakiness, sweating, confusion (esp. if on insulin/sulfonylurea) | Hypoglycaemia | Check glucose; review concurrent meds with prescriber |
If in doubt, seek care — don't wait for a private test
Red-flag symptoms need clinical assessment, not a home test kit. Contact your prescriber, NHS 111, or attend urgent care. Private blood tests are for planned monitoring, not emergencies.
Private monitoring: labs and costs
If your prescriber's monitoring is in place but you want to supplement it — for example, to add nutritional markers, to track more frequently, or because your private clinic does not arrange bloods — UK private labs offer suitable panels:
Medichecks — the primary recommendation here. Their Weight Management and Advanced Metabolic Health panels cover most of the monitoring markers above — HbA1c, lipids, kidney and liver function, and often thyroid and nutritional markers — with a doctor's report. Fingerprick home kit or clinic venous draw. Basic monitoring panels start around £49–£89, with fuller baseline panels around £99–£149.
Bluecrest Wellness — a solid alternative. Bluecrest metabolic and wellness panels offer broad coverage with in-person clinic appointments across the UK, which some people prefer to home fingerprick kits.
Randox Health — mentioned only as an additional option. Randox offers comprehensive health panels through UKAS-accredited labs with painless upper-arm (Tasso) self-collection; useful if you want their specific collection method, though their panels are not specifically tailored to GLP-1 monitoring.
| Panel type | Typical UK cost (2026) | Best for |
|---|---|---|
| Basic GLP-1 monitoring (HbA1c, lipids, kidney, liver) | £49–£89 | Routine 3-month checks |
| Full baseline / metabolic + nutritional | £99–£149 | Pre-treatment baseline; 6–12-month review |
| Comprehensive health check (incl. thyroid, FBC, vitamins) | £149–£299 | Thorough annual review |
NHS vs private monitoring — who is responsible?
This is the single most important practical point in this guide.
- NHS specialist obesity service prescription — monitoring is built into the programme. Baseline and follow-up bloods are arranged for you. You generally do not need to pay for private tests.
- Private clinic prescription — monitoring responsibility sits with the prescriber, but the depth of monitoring varies enormously between clinics. Some reputable private clinics arrange full baseline and follow-up bloods; some online services do little beyond an initial questionnaire. Ask explicitly what monitoring is included before you start. If the answer is "none", that is a meaningful safety gap, and either a better clinic or a properly planned private monitoring schedule (ideally with clinical review) is needed.
- Buying without proper prescriber oversight — strongly discouraged. The monitoring described in this guide assumes a prescriber who reviews your results and adjusts treatment. Tests without that clinical loop are far less useful and potentially unsafe.
Related guides
- Best blood test for weight loss & metabolic health UK — the broader metabolic-testing guide.
- Private diabetes / HbA1c test UK — understanding and tracking your HbA1c.
- Private thyroid panel UK cost — thyroid testing and the MTC-risk context.
- Liver health blood test UK — interpreting liver function tests.
- Private health check UK — comprehensive health-screen panels.
- HbA1c blood test guide — the science of HbA1c.
- Thyroid blood test guide — TSH and free T4 explained.
- Cholesterol & lipids test guide — reading your lipid profile.
- Liver function test guide — ALT, AST, GGT and friends.
- Private blood tests UK — pillar guide — the complete UK private testing playbook.