How to give a subcutaneous injection from a vial

This guide covers one setup: a multi-dose vial and a U-100 insulin syringe, the way most reconstituted peptides are drawn and injected. Pens and autoinjectors work differently and come with their own instructions; follow those. Nothing here replaces the instructions for your product or advice from your clinician. Read the Safety guide before a first dose.

What you need

• Your vial, mixed and labeled with the date. If you haven't mixed it yet, Start Here walks through it.
• A new U-100 insulin syringe, still sealed. A 0.3 mL (30-unit) or 0.5 mL (50-unit) syringe is easier to read for small doses than a 1 mL one.
• Alcohol swabs, and gauze or a cotton ball.
• A sharps container within reach before you start.

The steps, written out

1. Wash and check. Wash your hands with soap and water. Check the label: the right peptide, the right strength, the date you mixed it. The liquid should be clear, with nothing floating in it. If it's cloudy, colored or has specks, don't use it.¹
2. Clean the stopper. Flip off the plastic cap; the rubber stopper stays in. Wipe the stopper with an alcohol swab and let it air-dry.¹
3. Push in air. Pull the plunger back to your dose mark so the syringe holds that much air. Push the needle through the stopper and press the air into the vial. It keeps the vial from pulling against you as you draw.¹
4. Draw to your mark. Turn the vial and syringe upside down and keep the needle tip in the liquid. Pull slowly to a little past your mark, tap the barrel gently so any bubbles rise, then push back up to the mark exactly. Pull the needle out of the vial.¹
5. Pick a spot. Choose a site, and a spot within it you didn't use last time.¹ Start with clean, dry skin; if you wipe it with alcohol, let it dry fully first. Skip skin that is bruised, scarred, sore, red or hard, and never inject into lumps under the skin.²
6. Insert. With a 6 mm needle, most adults can go straight in at 90°. With an 8 mm or 12.7 mm needle, or if you're lean, gently lift a fold of skin between your thumb and index finger and insert into the middle of it. One smooth motion.^2,3,4
7. Push and hold. Push the plunger all the way down, slowly. Then leave the needle in for at least 5 seconds.¹
8. Out and press. Pull the needle out at the angle it went in, then let go of any fold. A small drop of liquid or blood is normal. Press with gauze for a moment; don't rub.¹
9. Sharps. Don't put the cap back on. The needle and syringe go straight into a sharps container.^1,5

Where to inject

Injections under the skin go into the fat layer, so the best spot is wherever you have the most of it. Vial instructions name the abdomen and the thighs, with the back of the upper arm when someone else gives the injection.¹ The needle-length research also measured the upper outer buttock, the hip.^3,4 Love handles aren't named in vial instructions, but they're a common choice for the same reason: a thick, easy-to-pinch layer of fat.

• Hip: the outer hip and upper outer buttock, below the hip bone. The thickest fat of the measured sites, on average 15.4 mm.³
• Love handles: the side of the waist, just above the hip bone. Usually a generous pinch of fat, even on people with a flat stomach. The studies here didn't measure it, so the guide's drawings use the abdomen's numbers for it.
• Abdomen: the belly, staying a couple of inches clear of the navel. The easiest to see and reach.¹ If you don't have much belly fat, the hip or love handles are a better choice: in the leanest people measured, the abdomen's skin-to-muscle distance was under 5 mm.⁴
• Thigh: the front and outer side, upper part. It's easy to reach, but it is the site where the muscle sits closest to the surface.⁴
• Back of the upper arm: midway down. Hard to reach and to lift a fold yourself, so it's best when someone else injects.¹

Move to a new spot every time. Injecting the same patch over and over can cause lipohypertrophy: rubbery, thickened lumps of fat under the skin. It is common, it changes how a drug is absorbed, and the fix is to stop injecting into those lumps and rotate properly.^2,7 A simple habit is to work around a site in a pattern, keeping each injection at least a finger's width from the last one.

How deep the needle goes

Ultrasound measurements in 388 adults found skin is about the same thickness everywhere people inject: on average 2.2 mm on the arm, 1.9 mm on the thigh, 2.2 mm on the abdomen and 2.4 mm on the upper outer buttock (the hip). The fat underneath varied far more: on average 10.8, 10.4, 13.9 and 15.4 mm at those sites, thicker in women and with higher BMI.³ Every needle on an insulin syringe gets through the skin. The question is whether it stops before the muscle.

A second study measured the distance from the skin's surface to the muscle in 341 adults. The middle value ran from 10.9 mm at the thigh to 16.9 mm at the buttock, but in the leanest people it was under 3 mm at the thigh. Going straight in without a fold, the authors estimated an 8 mm needle would reach muscle in 25% of thighs and 9.7% of abdomens, against 1.6% and 0.1% for a 4 mm needle. Angling a longer needle at 45° cut the risk but didn't remove it.⁴

That is why the injection-technique recommendations favor the shortest needles: 4 mm pen needles and 6 mm syringe needles are safe, work, and hurt less, and injecting into muscle is to be avoided.² The first study concluded that needles of 8 mm or longer, put straight in, may often reach muscle in the limbs of men and of anyone with a BMI under 25.³

Reading the syringe

Insulin-syringe markings are units of volume, not of drug: on a U-100 syringe, 100 units is 1 mL, so 10 units is 0.1 mL. How much peptide that holds depends entirely on how much water went into the vial, which is what the Dose & Mixing calculator works out. Read the mark where the flat front edge of the rubber stopper meets the scale, at eye level. Mixing up units and milliliters is the most common serious dosing error FDA describes with multi-dose vials: a 5-unit dose drawn as 50 units.

After the shot

A small drop of liquid or blood at the spot, a little redness, or a small bump that fades within a day is common. Note where you injected so the next one goes somewhere else.

Getting rid of needles

• Put each needle and syringe in a sharps container right after use, and keep the container away from children and pets.⁵
• When it's about three-quarters full, close it and follow your area's rules: drop-off sites such as pharmacies or doctors' offices, household hazardous waste sites, mail-back programs or special pick-up. Don't reuse the container.⁵
• Never throw loose needles in the trash or recycling, and never flush them.⁶
• Traveling? Take a small travel sharps container.⁵