Injections and Vial Care


If you have to self-administer injections for your HRT, it's essential to know how to do it safely, make it as painless as possible, and take care of your vial to prevent coring or other issues.


There are many different types of needles and syringes. Firstly, you should use something other than a non-detachable syringe that comes with the needle and syringe in one device. With these, you will be forced to draw from your vial and inject with the same needle. Drawing medication dulls the hand and will make injecting needlessly painful.

You will need to buy syringes, a larger gauge needle for drawing, and a smaller gauge needle for injecting, along with medical alcohol prep pads or wipes for sterilizing yourself and your vial. You should look for two types of syringes: luer lock or luer slip. Both will do the job. The main difference is that with luer lock syringes, the needle is twisted on, and luer slip syringes are pushed on. Regardless, you must buy matching needles, or you won't be able to connect them.

The higher the gauge a needle is, the thinner and less painful it will be, but it will also be slower to inject or draw. You should have a 21-23 gauge for drawing. The length doesn't matter. You should use a 1-1.5'' (25-38mm) 21-27G needle for injecting intramuscularly and a 0.5'' 25-31G needle for subcutaneous injections.

How to Draw Medication

Your vial contains a solution comprised of a carrier oil, typically MCT or castor oil for estradiol, preservatives such as benzyl benzoate and benzyl alchohol, and your estradiol dissolved in it. Your vial should state its concentration, for example, 40 milligrams per milliliter. You will figure out how much liquid you need to draw for your desired dosage by dividing your dosage by the concentration.

Firstly, take off the cap of your vial. This does not stay with your vial and should be thrown away. The rubber stopper is air-tight and will protect the medication. Next, take one of your alcohol wipes and clean the top of the vial; then, we will prepare your syringe. Unpackage one single-use syringe and drawing needle and attach them, avoiding touching the ends. Uncap the needle and draw up your dosage in air; this maintains pressure in the vial and makes drawing much easier. Stick your needle into the vial at a 45-degree angle, like in picture B. This significantly reduces the risk of coring (puncturing a hole in the vial).[1]

Inject the air into the vial and flip it upside down with the needle still in it. Now, slowly pull the plunger back to your desired dose; it should fill with liquid. If it doesn't, you may need to be patient, or you haven't put enough air into the vial and have created a vacuum. Tap the syringe to push any air bubbles to the top, and gently push them out of the syringe, though they are not usually dangerous. Once you have drawn up your medication, it's time to remove the syringe from your vial and inject.

Injecting Medication

When you have your medication in your syringe, you will face the needle up and swap the drawing needle for a higher gauge injection needle, carefully twist it off, put it into a sharps container, and attach the new needle.

Subcutaneous and intramuscular injections are relatively equally effective, and it is entirely up to personal preference which to do.[2]

Subcutaneous Injections

Subq injection locations[3]

Subcutaneous injections are when you use a shorter needle to inject medication between the skin and the muscle. This can be less painful but also more tedious. Subq injection sites can be seen in this section's attachment.

Prepare the site by wiping it with an alcohol prep pad and letting the alcohol dry before continuing. Pinch the skin between your thumb and index finger and hold it. Insert the needle into your skin at a 45-degree angle in a smooth motion, and push the plunger down. Wait a few seconds and pull the needle straight back out. Pat, do not wipe the area with an alcohol prep pad and put your favorite Band-Aid on it. Cap the needle and put it into your sharps container.

Intramuscular Injections

IM injection locations[4]

Intramuscular injections are when you inject directly into the muscle. They can be much faster than subq injections but also may leave bruising and hurt more. IM injections follow most of the same steps subq does. Im injection sites are listed in the attachment. Prep the site with an alcohol wipe and let it dry. Uncap and insert the needle at a 90-degree angle. Push the plunger down fully, wait a few seconds, and remove the needle. Now pat the area with an alcohol wipe and apply a Band-Aid. Some bleeding is normal and should be expected occasionally.[5]

Vial Shelf Life

A good rule of thumb with vials is that they last about two years; depending on exposure to light and heat exposure, they can sometimes be used for up to five years. It's best to store your vial away from sunlight in a room-temperature place like a drawer. Don't refrigerate and expose a vial to moisture.

Vial Coring

Another massive factor in vial shelf life is coring. The rubber stopper should be self-healing and close after every use, but if you draw too many times in the same place, at the wrong angle, or with too large of a needle, it can puncture a hole in the rubber. This is called coring. If your vial leaks has a visible hole or particles floating around it, do not inject from it. You can prevent coring by drawing correctly, like from the drawing section of this page, with a 21-23 gauge needle.

  1. Gragasin, Ferrante S. MD, PhD, FRCPC; van den Heever, Z. A. Neethling MB, ChB, DA (SA). The Incidence of Propofol Vial Coring with Blunt Needle Use Is Reduced with Angled Puncture Compared with Perpendicular Puncture. Anesthesia & Analgesia 120(4):p 954-955, April 2015. | DOI: 10.1213/ANE.0000000000000599
  2. Herndon, A. et al. (2023). Comparison of the Subcutaneous and Intramuscular Estradiol Regimens as Part of Gender-Affirming Hormone Therapy. Endocrine Practice, Volume 29, Issue 5
  5. Brand, Heather (Accessed November 11, 2023). "SUBCUTANEOUS (SUBQ) SELF-INJECTION VIDEO TRANSCRIPT" (PDF). Planned Parenthood.