Anatomy of injection supplies 

Injection supplies come in many different sizes, brands, and styles. For gender-affirming hormone therapy (GAHT, sometimes called HRT), injection supplies consist of three different components:

Barrel, sometimes referred to as a syringe


draw-up needle


Injection needle

Sometimes your pharmacy will give you these three different components as three separate packages (syringe, draw up needle, and injection needle). Other times, you may get it in less than three parts, such as when part of the syringe and needle are already attached to each other. As long as you have separate needles for drawing up and injection, the way in which it is dispensed shouldn't make a difference!

The needle is the part that you use to draw up your medication from the vial (using a larger draw-up needle), and also the part you use to inject yourself (using a smaller injection needle). You need two needles to inject your GAHT.

The length and gauge (g) of the draw-up needle and the injection needles are different. Each type will be used for a separate step of the injection process. 

Length refers to how long the needle is. 

Gauge is a number that refers to how “thick” the needle is. The thicker the needle is, the smaller the gauge number is. 

For drawing up medication, typical needle gauge sizes range from 18-21g. Drawing-up needle lengths range from 1-2 inches.

For intramuscular injections, typical needle gauge sizes range from 22-24g and 1-1.5 inches in length.

For subcutaneous injections, typical gauge sizes range from 25g-31g and are usually ⅝ of an inch in length. Even though subcutaneous injections could be performed with a needle that is longer than ⅝ inches long, it is not ideal or necessary, since you only need to insert the needle just under the skin.

The tip is where the syringe and needle attach to each other.

The needle hub is where the needles attach and detach from the syringe itself. This is important because if you are given injection supplies where the needle hubs cannot attach/detach from the syringe tips, you will not be able to use a separate needle for the drawing up and injection processes. When your injection supplies are dispensed, look at the needle hub to ensure that you have the right combination of needles and syringes to take your medication.

The barrel is the chamber inside the syringe that has measurement markings. This is where your medication will be drawn up into.


The plunger is at the end of the syringe and looks like a button. This is what you will use to both draw up the medication and push the medication through the needle for the injection itself.

Getting the right dose: how to read syringe markings

Your prescription is written as milligrams (mg) per milliliters (ml). Milligrams refers to the amount of medicine and milliliters refers to the amount of liquid. For example: If your provider ordered you 200 mg/ml of HRT and the instructions are to inject 0.5 ml once weekly from a 1 ml vial, that means there is 200 mg worth of medication inside the entire 1 ml of liquid. But since the instructions here are to only inject half (0.5 ml), your dose would be 100 mg.

Your provider has likely prescribed you 1 ml syringes or 100 unit syringes. Other times, you may be prescribed 3 ml syringes. Sometimes, your pharmacy may not have 1 ml/100 unit syringes in stock and will offer 3 ml syringes as a substitute.  Here is how to understand the markings and measure your dose on all three types of syringe:

How to read a 1 ml syringe

Each line is equivalent to 0.01 ml.  

Every 0.10 ml is marked with a larger line. 

For example, if your dose is .35 ml, you will draw up to the halfway point line between the .3 and .4 markings.

How to read a 3 ml syringe

Each line is equivalent to 0.10 ml.  

Every 0.5 ml is marked with a larger line. 

For example, if your dose is .25 ml, you will draw up the medication halfway between the second line (0.2 ml) and third line (0.3 ml) to draw up approximately 0.25 ml.

How to read syringes measured in “units” instead of ml

100 units is equal to 1 ml. Each line is equivalent to 2 units, or 0.02 ml.  

Every 10 units is marked with a larger line and is equivalent to .1 ml. 

For example, if your dose is .4 ml, you will draw up to 40 units.

Injection video tutorials

Want to see all of this in action? Check out our injection tutorial videos below featuring our very own Plume Cofounder and Chief Medical Officer, Dr. Jerrica Kirkley. Here, Dr. Jerrica will demonstrate and explain the proper injection supplies and self-injection techniques for both subcutaneous and intramuscular injections.

Intramuscular (IM) injection tutorial

Subcutaneous (SubQ) injection tutorial

Keep it clean!

It is crucial to always use a fresh, unused syringe and needle every time you do your injection. Never reuse your injection supplies. Dull needles make the injection extra painful, and you run the risk of developing an abscess or other complications. Keep it fresh and clean every time! 

In addition to using fresh injection supplies for each injection, remember to disinfect the top of your vials with a fresh alcohol swab before each injection. If you find yourself needing to use the last bit of medication from two different vials in order to draw up a full dose, you may alcohol-swab the top of BOTH vials and use the same drawing up needle for each vial.