What Retatrutide is and what it is studied for
Retatrutide is a single peptide that activates three receptors at once: GLP-1, GIP and glucagon. The first two are the mechanism tirzepatide uses — appetite down, gastric emptying slower, blood sugar steadier. The glucagon component is the addition; in research settings it is associated with higher energy expenditure, the likely reason retatrutide shows a stronger fat-loss signal than earlier single- and dual-agonists, with a better tendency to preserve lean mass.
It is studied for fat loss in people carrying meaningful excess weight, and secondarily for the markers that tend to move with it — HbA1c, liver enzymes, ApoB and triglycerides. The price of that power is the gut: nausea, reflux and fatigue in the first weeks are why people quit, and almost all of it is avoided by starting low and drinking water. The whole house protocol is built around those two habits.
Who it suits — and who should not run it
Written for adult women and men with real body fat to lose who will lift three times a week and hit a protein floor every day. Expect the compound to do everything on its own and the result is muscle loss dressed up as weight loss. It is not for people who are already lean, and never added on top of an existing GLP-1 medication. The house exclusions:
Not for
- Pregnant, breastfeeding, or planning pregnancy in the next 6 months.
- Personal or family history of medullary thyroid carcinoma or MEN2.
- History of pancreatitis, active gallbladder disease, or severe gastroparesis.
- Type 1 diabetes, or type 2 diabetes on insulin or sulfonylureas — hypoglycaemia risk; personalised protocol only, with the prescriber.
- A history of an eating disorder.
- Under 18, or a BMI under 22.
- Already on Ozempic, Wegovy, Mounjaro, Zepbound or similar — a switch is phased and belongs in a personalised protocol.
The house protocol
One injection a week, subcutaneous, in the abdomen a hand's width from the navel or the outer thigh, rotating sites. Sunday evening suits most people: side effects land on Monday–Tuesday and are gone by the weekend. One pen = 300 clicks; the 24 mg pen gives 80 mcg per click and the 12 mg pen 40 mcg per click, so the same milligram dose is simply double the clicks on the smaller pen.
Three phases: weeks 1–4 ramp (step up 0.5 mg a week only if the previous week was comfortable), weeks 5–8 hold on the week-4 dose, weeks 9–12 consolidate with one optional step if week-8 labs and tolerance allow.
| Pen | Dose per injection | Clicks | Frequency | Timing | Cycle |
|---|---|---|---|---|---|
| Retatrutide 24 mg (80 mcg/click) · women | 1.5 → 2.0 → 2.5 → 3.0 mg | 19 → 25 → 31 → 38 | Once weekly | Sunday evening | Weeks 1–4 ramp |
| 24 mg · women | 3.0 mg hold · optional 3.5 then 4.0 mg | 38 · optional 44 then 50 | Once weekly | Sunday evening | Weeks 5–8 hold · 9–12 consolidate |
| Retatrutide 24 mg (80 mcg/click) · men | 2.0 → 2.5 → 3.0 → 3.5 mg | 25 → 31 → 38 → 44 | Once weekly | Sunday evening | Weeks 1–4 ramp |
| 24 mg · men | 3.5 mg hold · optional 4.0 then 4.5 mg | 44 · optional 50 then 56 | Once weekly | Sunday evening | Weeks 5–8 hold · 9–12 consolidate |
| Retatrutide 12 mg (40 mcg/click) | Same mg as above | Double: women 38 → 50 → 62 → 75, then 88 → 100 · men 50 → 62 → 75 → 88, then 100 → 112 | Once weekly | Sunday evening | 12 weeks, same phases |
Pens per cycle: women use 36.5 mg, men 42.5 mg — 2 pens of 24 mg (about 11 mg left for women, 5 mg for men) or 4 pens of 12 mg. Doses on the 12 mg pen run past 100 clicks: count in tens, and if a pen runs out mid-dose, note the clicks taken and finish from the new one.
The hold rule. Any week with meaningful nausea, vomiting, dizziness or constipation is a hold week: repeat the dose, do not step up. Two hold weeks in a row means going back one step. If side effects are more than mild, split the weekly dose — half on Sunday, half on Wednesday, same total clicks. Splitting is the single most effective fix for nausea; never step up in a week you have just split. Keep the pen in the fridge between uses.
Week by week — what people typically notice and when
| When | What is typically reported |
|---|---|
| Weeks 1–2 | Appetite drops within about 48 hours. Mild nausea on day 2–3, some tiredness. The scale moves 1–2 kg, mostly water. |
| Weeks 3–4 | The "quiet food noise" effect is fully there. Most people are 3–4 kg down. |
| Weeks 5–8 (hold) | Steady 0.5–1 kg a week. Energy returns. The waist moves more than the scale; week-8 labs decide the next step. |
| Weeks 9–12 | Consolidation. Typical 12-week results in research settings are 8–12 % of body weight; protein and training explain more of the spread than dose does. |
| Any week | Losing faster than 1 % of body weight a week is a sign to eat more protein, not a success. |
Weigh in once a week. Walking 8–10 k steps a day and three full-body resistance sessions — keeping the weights you lifted before the cycle — are part of the protocol, not extras. No new endurance programme during the ramp; train on a small meal, never fasted, for the first four weeks.
Labs we ask for before and during
| Marker | When | Why it is on the list |
|---|---|---|
| HbA1c, fasting glucose, fasting insulin | Baseline · week 8 · week 12 | Glucose response; hypoglycaemia risk alongside other glucose-lowering medication |
| Lipid panel (ApoB, LDL, HDL, triglycerides) | Baseline · week 12 | Retatrutide typically improves these; the repeat confirms it |
| ALT, AST, GGT, bilirubin | Baseline · week 8 | Liver — tends to fall as liver fat falls |
| Cystatin C (never creatinine alone) | Baseline · week 12 | Kidney measure not distorted by muscle or creatine |
| Lipase | Baseline | Pancreas baseline before any incretin |
| TSH, free T4 | Baseline | Thyroid before a metabolic compound |
| Full blood count, ferritin | Baseline | Anaemia and iron stores affect energy and the HbA1c reading |
| Blood pressure, resting heart rate | Weekly at home | Heart rate typically rises 5–10 bpm; blood pressure falls |
Same lab, same time of day, before the injection, not the day after training — otherwise the week-8 decision is made on noise. Vitamin D, magnesium and omega-3 are the only general supplements.
Stacking: what it pairs with
Retatrutide runs alone in its class: never stacked with tirzepatide or any other GLP-1 compound — same receptors, and the gut pays twice. Moving between them is a phased switch for a personalised protocol.
What pairs sensibly is support for the lean mass the cycle puts at risk: a nightly CJC-1295 + Ipamorelin pairing for recovery and body composition, or tesamorelin when the visceral depot is the target. Any stack means more labs, not fewer — IGF-1 joins the list the moment a GH secretagogue is involved.
Common mistakes
- Starting at the hold dose. Week 1 is 1.5 mg (women) or 2.0 mg (men) — 19 or 25 clicks on the 24 mg pen. Skipping the ramp is the fastest route to a week of vomiting.
- Not drinking. Retatrutide slows the stomach and blunts thirst at the same time. Three litres a day, electrolytes on training and nausea days, and no greasy food or alcohol on injection day.
- Under-eating protein. 1.6–2.0 g per kg of goal body weight, every day. Below 1,200 kcal (women) or 1,500 kcal (men) on average is muscle loss, not progress.
- Confusing the pens. 38 clicks is 3.0 mg on the 24 mg pen and 1.5 mg on the 12 mg pen. Check which pen is in your hand.
Frequently asked questions
How many clicks is a retatrutide dose on the 24 mg pen?
The 24 mg pen holds 300 clicks at 80 mcg per click. The house protocol starts at 19 clicks (1.5 mg) for women or 25 clicks (2.0 mg) for men, steps up weekly to a hold of 38 or 44 clicks, with an optional late step to 50 or 56 clicks.
What is the difference between the 24 mg and 12 mg retatrutide pens?
Only concentration. The 12 mg pen delivers 40 mcg per click, so every dose is exactly double the clicks — 38 instead of 19 for 1.5 mg. A cycle takes 2 of the 24 mg pens or 4 of the 12 mg pens.
When should I inject retatrutide?
Once a week, same weekday, subcutaneously in the abdomen or outer thigh. Sunday evening suits most people: any nausea lands on Monday–Tuesday and clears by the weekend.
What do I do if the nausea is more than mild?
Hold — repeat the same dose next week instead of stepping up. If it stays more than mild, split the weekly dose: half on Sunday, half on Wednesday, same total clicks. Two hold weeks in a row means going back one step.
Which labs do I need before starting retatrutide?
HbA1c with fasting glucose and insulin, a lipid panel, liver enzymes, cystatin C, lipase, TSH with free T4, and a full blood count with ferritin. HbA1c and liver enzymes are repeated at week 8, most of the panel again at week 12.
Want this written for your body, not the average one?
The personal research protocol (€399, follow-up included) takes your intake, puts it through human review, and returns a short results version plus the full clinical document — then a free coach call on WhatsApp to walk it through and read your labs against the plan.
Build my protocol Book a 15-minute call