Triple agonist · Investigational, not licensed in the UK
Before you read on
Retatrutide is not licensed for use in the UK, or anywhere else, at the time of writing. TrueVitals does not supply, prescribe, recommend or endorse it, and does not endorse buying unlicensed peptides online. This page exists because people are taking it, on clinical trials and outside them, and the ones who are should at least know what it does to their blood and what to watch. If you are on a trial, your trial team's monitoring comes first. If you obtained it elsewhere, please tell a doctor.
Retatrutide acts on three receptors: GLP-1 and GIP, like Mounjaro, plus glucagon, which is the part that makes it different and the part that changes what you need to monitor. The glucagon action pushes the liver to burn energy, raises heart rate, and can move glucose and liver enzymes in ways the two-receptor drugs do not. Everything true of GLP-1 monitoring still applies, with a closer eye on the liver, kidneys, glucose and muscle.
Venous draw at 103 UK clinics or at home. Report within 48 hours of the lab receiving your sample. We test; we do not prescribe.
Last reviewed 15 September 2026
The short answer
If you are taking retatrutide, monitor the full GLP-1 set (HbA1c, fasting insulin, lipids with ApoB, ferritin, B12, vitamin D, thyroid, albumin) and pay extra attention to four things the glucagon action can move: liver enzymes, kidney function with cystatin C, glucose control, and lean muscle. Test before starting if you have not already, then every three months. A blood test cannot verify what is in an unlicensed vial; it can only show you what it is doing.
Our position
TrueVitals is a blood testing company. We will test anyone's blood and explain the results honestly, whatever they are taking. That is not the same as endorsing what they are taking. Unlicensed peptides bought online have no guarantee of identity, dose, purity or sterility, and the safety data on retatrutide comes from supervised trials with regular clinical monitoring that a home user does not have. If that is your situation, the most useful thing this page can do is persuade you to involve a doctor.
What is different
Semaglutide works on GLP-1. Tirzepatide adds GIP. Retatrutide adds glucagon on top, and glucagon is not a subtle hormone. It tells the liver to release and burn energy, which is a large part of why the weight loss in trials was bigger, and it does three other things worth knowing. It raises heart rate, which was seen consistently in phase 2. It can push blood glucose up in the short term, which the GLP-1 and GIP components then counteract, so glucose control in the first weeks can be less predictable than on the other drugs. And it works the liver hard, which in trials showed up as transient rises in liver enzymes in some participants, alongside dramatic improvements in liver fat. None of this is a reason to panic. It is a reason to test rather than guess.
The other difference is speed. Faster weight loss means faster depletion of iron, B12 and vitamin D, more gallstone risk, and more lean mass lost if protein and resistance training are not deliberately protected. Every problem the GLP-1 pages describe arrives sooner. Why people get tired on GLP-1s, and what to test.
What to monitor
| Marker | Why it matters on a triple agonist | Watch for | Panel |
|---|---|---|---|
| ALT, AST, GGT, ALP, bilirubin | Glucagon works the liver directly; trials saw both rapid liver-fat improvement and transient enzyme rises | ALT or AST more than three times the upper limit, or rising month on month; raised ALP and bilirubin with pain under the right ribs (gallstones) | All panels |
| Creatinine, eGFR, cystatin C, urea | Dehydration and rapid muscle loss both distort creatinine; cystatin C separates the two | Creatinine falling while cystatin C is flat (muscle loss); urea rising with a normal cystatin C (dehydration); cystatin C rising (true kidney change) | Creatinine and eGFR in all; cystatin C in Ultimate and Signature |
| HbA1c, fasting glucose, fasting insulin | Glucagon can raise glucose while the incretin components lower it; the net effect is a fall, but the path is less predictable | Hypo symptoms if you also take insulin or a sulfonylurea; HbA1c not falling by month three | HbA1c and glucose in all; fasting insulin and HOMA-IR in Ultimate and Signature |
| Sodium, potassium, magnesium | Nausea, reduced intake and fluid shifts; heart-rate increase makes electrolytes matter more | Low potassium or magnesium with palpitations | All panels |
| ApoB, triglycerides, HDL, Lp(a) | Cardiovascular benefit is the point; ApoB is the measure | ApoB not moving despite large weight loss (look at Lp(a)) | ApoB in all; Lp(a) in Ultimate and Signature |
| Ferritin, B12, folate, vitamin D | Depleted faster than on a GLP-1 alone because intake falls further and faster | Any downward trend between tests; ferritin below 30 | All panels |
| Albumin, total protein | The blood-test signal that protein intake is not keeping up with the rate of loss | Falling albumin alongside falling creatinine | All panels |
| TSH, free T4, free T3 | Large, fast weight loss changes levothyroxine requirements; thyroid disease mimics drug fatigue | TSH drifting; free T3 at the floor | All panels |
| hs-CRP | Should fall as visceral fat goes; a rise is a warning | Rising hs-CRP, especially with liver or gallbladder symptoms | All panels |
| Testosterone, oestradiol | Very rapid fat loss and low protein can suppress sex hormones; in men testosterone often rises overall | A fall alongside fatigue and low mood | Core hormones in Advanced; complete set in Ultimate and Signature |
Heart rate and blood pressure are not blood markers but were the most consistent findings in the phase 2 data. Track them at home. Guides: liver, kidney and cystatin C, HbA1c, ApoB, ferritin, B12, vitamin D, thyroid.
What a blood test cannot do
Limit 1
A blood panel measures your physiology, not the product. If what you bought is underdosed, contaminated, or not retatrutide at all, the blood test will show the effect, not the cause. Only a trial or a pharmacy supply chain gives you the product itself.
Limit 2
Phase 3 participants get ECGs, supervised dose escalation and a clinician who can stop treatment. A quarterly blood test is a fraction of that. It is far better than nothing, and it is still not the same.
Limit 3
Normal results on a panel do not mean the drug is safe for you long term. The long-term data does not exist yet for anyone. That is what licensing is for, and it has not happened.
Which panel
Advanced
74 biomarkers · £269
Full liver panel, kidney, electrolytes, HbA1c and glucose, ApoB and lipids, ferritin, B12, folate, vitamin D, full thyroid, albumin, hs-CRP. Everything except fasting insulin, cystatin C and Lp(a).
View AdvancedThe triple-agonist panel
Ultimate
114 biomarkers · £349
Adds cystatin C (muscle versus kidney), fasting insulin and HOMA-IR (the glucose picture glucagon complicates), Lp(a), complete hormones and tumour markers. The only panel that covers every row in the table above.
View UltimateHealth plans
2, 3 or 4 tests · from £706
Quarterly testing bought upfront at a lower price per test, each report compared against the last. The trend is the whole point on a drug this fast.
View health plansClinic draw £19. At-home £39. Fast from 10pm the night before. Pay monthly available.
FAQs
No. As of September 2026 it is an investigational medicine in phase 3 trials and is not licensed by the MHRA or any other regulator. Anything sold as retatrutide in the UK outside a trial is unlicensed and unregulated. TrueVitals does not supply or endorse it.
Yes. We test blood and explain results for anyone, and your report will be honest about what it shows. Testing your blood is not an endorsement of what you are taking, and we would rather you were doing this under a doctor's supervision.
The glucagon receptor. It works the liver harder, raises heart rate, can move glucose unpredictably early on, and drives faster weight loss, which depletes nutrients and muscle faster. Monitor the same markers as for any GLP-1 with closer attention to liver enzymes, cystatin C, glucose control and albumin.
A baseline before starting, then at least every three months. On a trial, follow the trial schedule; this is in addition, not instead.
No. A panel measures the effect on your body, not the contents of the vial. If results are not moving in the way the trial data would predict, that is one possible reason, but it is not proof either way.
Yes: nothing but water from 10pm the night before with a morning appointment, so that fasting glucose, insulin and lipids are accurate. Full preparation guide.
One venous draw, 114 biomarkers, a report within 48 hours that reads liver, kidney, glucose, nutrients and muscle together. And a conversation with a doctor, please.
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