How do you inject retatrutide?

Retatrutide is injected subcutaneously (into the fat layer beneath the skin) once weekly. Remove from the fridge 30 minutes before use, wash hands, clean the injection site with an alcohol swab, allow to dry, pinch the skin, insert the needle at 45 to 90 degrees depending on body fat level, inject slowly over 5 to 10 seconds, hold in place for 10 seconds after completing the dose, then withdraw and dispose safely in a sharps container.

Where do you inject retatrutide?

Retatrutide is injected into one of three approved subcutaneous sites: the abdomen (most preferred — at least 5cm from the navel), the outer upper thigh, or the back of the upper arm. The abdomen is generally recommended first due to its faster and more consistent absorption profile — abdominal subcutaneous blood flow runs over 30% higher than thigh blood flow. Rotate between sites weekly.

What needle size do I need for retatrutide?

The recommended needle gauge for retatrutide is 29 to 31 gauge (thinner needles for less pain) with a length of 8mm for most adults. Patients with very low body fat may need to inject at a 45-degree angle to avoid intramuscular injection. Never reuse needles — always use a fresh sterile needle for each injection.

How do I store retatrutide?

Store retatrutide refrigerated at 2 to 8°C in the original packaging until use. Once removed from the fridge, retatrutide can be stored at room temperature up to 30°C for up to 28 days. Never freeze retatrutide — frozen peptides are permanently compromised and must be discarded. Keep away from direct sunlight and heat sources.

How often do I rotate retatrutide injection sites?

Rotate retatrutide injection sites with every weekly injection. Move at least 2.5cm from the previous injection spot within the same area, and alternate between body regions across weeks. Poor site rotation leads to lipohypertrophy — thickened fatty tissue at overused sites — which reduces medication absorption by 20 to 30% and creates inconsistent dosing.

How to Inject Retatrutide: 7 Proven Steps for Safe First Injection

Knowing how to inject retatrutide correctly is essential for getting consistent results from this powerful triple agonist medication. Unlike Mounjaro which uses a built-in auto-injector pen, retatrutide from Mymetabolism is supplied as a research peptide requiring subcutaneous injection with a separate syringe and needle. The technique is simple and takes under five minutes once learned — but injection site selection, rotation, needle choice, and a few key steps make a significant difference to comfort, absorption consistency, and long-term tissue health. This guide covers everything you need to know about how to inject retatrutide safely and effectively.

All injection technique guidance in this article follows standard subcutaneous injection principles consistent with the clinical trial administration protocols documented in the retatrutide TRIUMPH programme and general NHS clinical guidance. Contact our 24/7 support team with any questions before or after your first retatrutide injection.

What you need before you inject retatrutide

How to inject retatrutide guide — retatrutide injection supplies syringe alcohol swab sharps container UK Mymetabolism 2026 — Having everything prepared before starting the injection removes the most common causes of errors and ensures a calm, correct technique every time.

Gather all supplies before starting. Having everything to hand removes the need to pause mid-injection and ensures the process is calm and correct. You will need:

Your retatrutide vial — inspected and at room temperature (30 minutes out of fridge)
A sterile 1ml syringe with a 29 to 31 gauge, 8mm needle
Two alcohol swabs — one for the vial stopper, one for the injection site
A sharps container for safe needle disposal
A clean cotton ball or gauze pad
A record of your last injection site for rotation purposes

Retatrutide injection sites — where to inject

The three approved subcutaneous injection sites for retatrutide are the abdomen, the outer upper thigh, and the back of the upper arm. The abdomen is recommended as the primary site for most patients learning how to inject retatrutide for the first time:

Abdomen (most preferred): inject into the soft fatty tissue at least 5cm from the navel, on the left or right side. The abdomen is preferred because abdominal subcutaneous blood flow runs over 30% higher than thigh blood flow — producing faster and more consistent retatrutide absorption. It also offers the largest total injection area of any site, allowing 15 to 20 distinct injection points before revisiting the same spot
Outer upper thigh: inject into the front outer portion of the thigh, midway between the hip and knee. Absorption is slightly slower from the thigh than the abdomen but this is a practical and comfortable alternative, particularly for abdominal rest weeks
Back of upper arm: inject into the fatty tissue at the back of the upper arm. This site may require assistance for self-injection. Not recommended as the sole site — combine with abdomen and thigh rotation

Never inject into areas with active bruising, redness, hardness, scars, or moles. These areas impair absorption and increase the risk of complications.

7 proven steps to inject retatrutide

Step 1: Remove from fridge 30 minutes before

Allow your retatrutide vial to reach room temperature for 30 minutes before injecting. Cold peptide solutions cause significantly more stinging and discomfort at the injection site. Never accelerate warming with heat, microwaves, or warm water — allow the vial to warm naturally at room temperature. This is the first and simplest step in learning how to inject retatrutide comfortably.

Step 2: Wash hands and prepare supplies

Wash hands thoroughly with soap and water for at least 20 seconds. Dry completely with a clean towel. Lay all supplies on a clean, flat surface. Check the vial — the solution should be clear, colourless or very slightly yellow, with no visible particles or cloudiness. If the solution is cloudy, discoloured, or contains particles, do not use it. Contact our support team for a replacement.

Step 3: Clean the vial and draw the dose

Wipe the rubber stopper of the retatrutide vial with a fresh alcohol swab. Allow to dry for 10 to 15 seconds — never blow on it. Draw air into the syringe equal to your dose volume. Insert the needle through the rubber stopper and inject the air into the vial — this prevents a vacuum forming. Invert the vial and draw the medication slowly to avoid bubbles. Hold the syringe upright, tap gently to move any air bubbles to the top, and push the plunger slowly to expel them. Verify the correct dose amount before withdrawing the needle.

Step 4: Clean the injection site

Using a fresh alcohol swab, clean the injection site using a circular motion from the centre outward. Allow to dry completely for at least 10 to 15 seconds before injecting — injecting into wet alcohol stings on entry and increases irritation risk. Select the site based on your rotation schedule — checking your injection log before proceeding.

Step 5: Pinch and insert the needle

Pinch a fold of skin firmly between thumb and forefinger, pulling the fatty tissue slightly away from the underlying muscle. This is particularly important for leaner patients and thigh injections to ensure subcutaneous rather than intramuscular delivery. Insert the needle at 90 degrees for patients with adequate subcutaneous fat, or at 45 degrees for leaner patients. The needle should enter smoothly and with minimal resistance — if you feel significant resistance, you may have hit scar tissue or a blood vessel. Withdraw and choose a different spot.

Step 6: Inject slowly and hold for 10 seconds

Depress the plunger slowly and steadily over 5 to 10 seconds to deliver the full dose. Rapid injection causes more pain and can affect absorption. Once the full dose has been delivered, hold the needle in place for at least 10 seconds before withdrawing. This is one of the most commonly missed steps in learning how to inject retatrutide — medication leakback through the puncture site occurs most commonly in the first 5 to 8 seconds after delivery if the needle is withdrawn too quickly.

Step 7: Withdraw and dispose safely

Withdraw the needle smoothly in the same direction it was inserted. Apply gentle pressure with a clean cotton ball or gauze — do not rub. A small drop of blood at the injection site is completely normal. Place the used needle and syringe directly into your sharps container — never recap, bend, or dispose of needles in household waste. Record the injection date, dose, and injection site in your log for rotation tracking.

Rotation schedule for retatrutide injections

Site rotation is one of the most important and frequently neglected aspects of knowing how to inject retatrutide correctly. Lipohypertrophy — thickened, hardened subcutaneous fat at overused injection sites — reduces medication absorption by 20 to 30% and creates inconsistent dosing. A four-week rotation across three body sites eliminates this risk:

Week 1: right side of abdomen
Week 2: left outer thigh
Week 3: left side of abdomen
Week 4: right outer thigh
Week 5: return to week 1 — each site has had 3 weeks to recover

Move at least 2.5cm from the previous injection point within any given area. Keep a written or app-based log — a note in your phone with the date, dose, and site takes 10 seconds and prevents the tissue damage that inconsistent rotation causes over time.

Needle size for retatrutide injections

Needle gauge	Needle length	Best for	Notes
29G	8mm	Most adults with moderate body fat	Good balance of flow rate and pain
30–31G	8mm	Recommended — most comfortable	Thinner needle, minimal pain, standard subcutaneous depth
31G	4–6mm	Very lean patients or abdominal injections	45-degree angle required — prevents intramuscular delivery

How to store retatrutide

Unopened vials: refrigerate at 2 to 8°C in original packaging. Keep away from the fridge back wall (freezing risk) and fridge door (temperature fluctuation)
After removal from fridge: store at room temperature up to 30°C for up to 28 days. Label the vial with the date first removed from fridge
Never freeze: frozen peptides are permanently structurally compromised and must be discarded — freezing cannot be reversed
Travelling: use an insulated medical travel wallet with a buffered ice pack. Never place ice directly against the vial

For the full storage guide covering all GLP-1 medications, see our How to Store GLP-1 Medications guide.

Common retatrutide injection mistakes to avoid

Withdrawing the needle too quickly — the most common cause of dose leakback. Always hold for 10 seconds after completing delivery
Injecting into cold medication — causes unnecessary stinging. Always allow 30 minutes at room temperature
Reusing needles — compromises sterility and significantly worsens injection site pain. Always use a fresh sterile needle
Injecting too close to the previous site — the primary driver of lipohypertrophy. Always move at least 2.5cm
Injecting at 90 degrees when lean — risks intramuscular injection which changes the absorption profile. Use 45-degree angle for lean patients or short needles
Not drying the alcohol swab site — injecting into wet alcohol causes unnecessary stinging
Disposing of needles in household waste — never do this. Sharps containers are required by law in the UK

For the complete context on retatrutide — including TRIUMPH-1 results and UK availability — see our Retatrutide 2026 guide. Browse our full product range and see our other injection guides for Mounjaro, Ozempic, and Wegovy.

Written by the Mymetabolism Team UK-based weight management experts · Verified GLP-1 supplier · 2,400+ customers served

How to inject retatrutide — 7 proven steps for a safe first injection.