How and where to inject testosterone

Thinking about testosterone replacement therapy (TRT) to boost your energy or libido? Injections are the original—and still one of the most effective - ways to get testosterone into your system. Gels, patches and pills are available too, but many men (and their doctors) stick with injections because they deliver reliable results and put you in control.

Here’s our guide for beginners on taking TRT safely and how to make it as painless as possible.

Key takeaways

• Most men look into TRT because they feel low in energy, mood, libido or strength.
• Testosterone injections are a common form of TRT and should only be started after confirming low levels with a blood test and medical guidance.
• Injections are given either intramuscularly (typically in the glute or thigh) or subcutaneously (into belly fat).
• Safe technique is essential: use sterile equipment, clean the vial and skin with alcohol, inject slowly, never reuse needles, and dispose of sharps properly.
• Injection frequency depends on the specific testosterone type prescribed, and consistency matters more than time of day.
• Seek medical advice if you experience unusual pain, swelling, dosing errors, or feel unwell.

Injecting testosterone: A step-by-step guide

Most men look into TRT because they feel low in energy, mood, libido or strength. But getting a blood test (you can order an at-home one through Voy) to check your T levels is key before you start TRT, as there are other causes of these symptoms.

If your doctor thinks TRT might be a good fit for you, here’s how to inject it safely:

Step 1: Set up your equipment

• Choose a clean, comfortable, well-lit area for your injection.
• Gather all supplies (testosterone vial or ampoule, syringe(s), needle(s), alcohol swabs, gauze, sharps container).
• Check the expiration date on your testosterone and ensure the solution is clear (no cloudiness or particulate matter).
• Wash your hands thoroughly with soap and water.

Step 2: Pick your injection site

The most common injection sites include:

• Gluteal (buttock) muscle
• Thigh (quadriceps) muscle
• Abdomen (subcutaneous fat)

Some guys prefer to inject into the deltoid (shoulder) muscle, but this is less common.

We’ll discuss the pros and cons of each site further below.

Step 3: Choose your needle type

At Voy, we use 29G or 27G needles for injecting testosterone, as these are smaller needles which tend to be more comfortable.

Some clinics may offer a 25G or 23G needle, which are thicker, but can make drawing up testosterone faster.

Step 4: Prepare the injection

• If your medication comes in an ampoule, carefully snap it open (you can use your fingers or an ampoule breaker).
• If you have a separate needle and syringe, open these carefully without touching the connecting ends and attach them together. Always use new, sterile needles and syringes.
• If your testosterone is in a vial, alcohol wipe the rubber stopper and insert your needle.
• Leave the cap on the needle until you’re ready to use it. Be careful not to touch the needle against anything.
• Insert the needle into the vial or ampoule and pull back on the plunger. Draw up the dosage recommended by your doctor. This may take a few minutes if you are using a thin needle. Warming the vial or ampoule in your hand or warm water will speed up this process.

Step 5: Inject your testosterone

• Clean the injection site with an alcohol wipe and ensure that nothing touches the area before injecting.
• Insert the needle.
• If injecting into muscle, pull back gently on the plunger to check for blood. If you see blood, withdraw, discard, and start again at a new site.
• Push the plunger down slowly.
• Remove the needle and hold the gauze or an alcohol wipe to the injection site for 10 seconds to prevent leakage.

Step 6: Dispose of your needles

Immediately dispose of your needle, syringe, broken ampoules, etc., into a sharps container.

Where to inject testosterone (best places)

You can safely inject testosterone in several places. Below are common injection sites and typical needle recommendations.

Glute injection site (intramuscular)

Your glutes (the main muscles in your bum) are the most common site for TRT, as injecting here tends to be the least painful spot. The best needle size for glute injection is usually 25G or 27G, with a length of 1 inch or more (depending on your size).

Insert the needle below your pelvis in the section furthest away from your spine.

Quad/thigh injection site (intramuscular)

If you struggle to inject into your glute because of mobility issues or other reasons, your quads (the leg muscles at the front of your thigh) can work really well. The best needle size for quad/thigh testosterone injections is 25G or 27G, with a length of 1 inch or more.

Inject into the middle-outer part of your thigh.

Abdomen/belly fat (subcutaneous)

Injecting into your belly fat is also known as the subcutaneous route. Fine needles (27–29G) work best. Many clinics now recommend injecting TRT this way because it gives a smoother testosterone release meaning fewer peaks and crashes.

Shoulder (intramuscular)

Some men prefer to inject into their shoulder, though it’s not what we’d recommend. It’s a smaller muscle, compared to your glutes or quads, so there's a higher risk of hitting a nerve or major blood vessels. Most clinics steer men away from this injection site.

What size needle to inject testosterone in shoulder?

The best needle size for shoulder testosterone injections is 29G or 27G, 0.5 to 1 inch.

Where not to inject testosterone

There are some areas of the body where injecting testosterone is a really bad idea.

Don’t inject testosterone into:

1. Your veins or major blood vessels: This is really dangerous as the oil from the medication can lead to blockages in your heart, lungs or capillaries.

2. Your groin or genitals: Injecting testosterone into this area will not improve absorption and is very dangerous.

3. Your neck, hands, arms, feet, back or lower legs: These areas are highly dangerous to inject into because there’s a risk of hitting a blood vessel or nerve.

What happens if testosterone is not injected into the muscle?

Injecting subcutaneously (belly fat) is fine and some clinics even prefer it. You’ll likely get a slower, more stable release of testosterone.

But injecting into random spots or shallow tissue isn’t recommended. Expect poor absorption, irritation, or just wasted effort. Stick to the approved sites and always ask your doctor if you’re unsure.

How often should you inject testosterone?

Your TRT injection schedule depends largely on the testosterone ester (e.g., testosterone undecanoate, cypionate, enanthate, propionate) you’ve been prescribed. Your doctor will tell you how often to inject your TRT.

Shorter-acting esters often require two or three weekly injections to smooth out hormone fluctuations.

There is no universal “best time of day” to inject. Consistency and timing that fits your lifestyle are more important.

Safety and tips to reduce pain and discomfort

There are a few ways to make injecting TRT safer and more comfortable:

• Never reuse any needles or syringes.
• Wash your hands before starting.
• Always clean the skin with an alcohol wipe. Let it dry before injecting to avoid stinging.
• Warm the testosterone vial or ampoule before drawing up/injecting.
• Insert quickly, withdraw smoothly.
• Put any used needles directly into a sharps bin to avoid injuries.

How to draw testosterone from a vial easily?

Sometimes drawing the thick testosterone oil can be difficult when using a thin injection needle.

These tips will make drawing up faster and easier.

1. Warm the vial in your hands or warm water before starting.

2. Pull back the plunger further than you expect, whilst maintaining tension, to improve the suction caused by the plunger vacuum.

3. Tilt the syringe at a 30-degree angle so that the oil draws out of the needle in a flow, rather than dripping. This increases the speed of the draw by reducing resistance.

Common mistakes to avoid

Here are some rookie mistakes you should do your best to avoid when you start TRT:

• Injecting too fast
• Pushing down too hard on the plunger, when using a separate syringe/needle, causing the needle to come off
• Not pulling back enough on the plunger, which reduces the draw speed
• Trying to draw up cold oil, which is thicker (warm the vial up first using your hands)
• Not reading the dose properly, or misunderstanding the volume on the syringe

When to seek medical advice

Always seek medical advice if:

• You aren’t sure of how to inject or what dose you should be injecting.
• You feel unwell after injecting.
• The injection site becomes red, warm, swollen or painful.
• You injected more or less than your prescribed dose.
• You experience nerve pain, tingling or numbness at or around the injection site.

Could TRT be a good fit for you?

Wondering if low testosterone is holding you back? Boost your energy, drive and strength with a tailored testosterone plan built by leading TRT doctors.