How to Inject Tirzepatide and Semaglutide: GLP-1 Guide

You have done the intake, your provider has reviewed your information, and your medication has arrived. The next question most people have is not about the science. It is a practical one: how do you actually do this?

Subcutaneous injection is not difficult, but it is a skill. The first injection is the most intimidating. By the third or fourth, it takes less than a minute. This guide covers everything you need to know to inject GLP-1 medications safely and comfortably: technique, injection site selection, storage, and how to handle the issues that come up for most patients in the first few weeks.

If you are on a compounded semaglutide or tirzepatide program, your care team is available to answer questions about your specific formulation. This guide covers general best practice. Your provider’s written instructions take precedence over anything here.

What you need before you start

Before your first injection, verify that you have:

• Your medication vial (confirm it has been refrigerated and is within its use-by period)
• Syringes appropriate for subcutaneous injection (typically 1mL insulin syringes with a 29-31 gauge, 4-6mm needle)
• Alcohol swabs
• A sharps disposal container

Do not use a needle that has been used before. Do not use medication from a vial that looks cloudy, discolored, or has visible particles. GLP-1 medications in compounded form are typically clear and colorless.

Letting the medication come to room temperature

Cold medication stings more. This is not dangerous, but it is uncomfortable and entirely avoidable. Before drawing your dose, take the vial out of the refrigerator and let it sit at room temperature for 15 to 30 minutes. If you forget, you can hold the filled syringe in your closed hand for a minute or two before injecting. Do not apply heat directly to the vial.

Step-by-step injection technique

Step 1: Wash your hands. Use soap and water for at least 20 seconds. This is the single most important infection prevention step.

Step 2: Clean the vial top. Wipe the rubber stopper of the vial with a fresh alcohol swab. Let it dry for 10-15 seconds before inserting the needle.

Step 3: Draw the correct dose. Pull the plunger back to draw air into the syringe equal to your prescribed dose. Insert the needle into the vial and push the air in (this creates pressure that makes drawing easier). Invert the vial and pull the plunger back to your prescribed dose. Check your provider instructions for the exact volume in mL or units.

Step 4: Remove air bubbles (optional but recommended). Hold the syringe needle-up and tap the barrel to move bubbles to the top. Gently press the plunger until the bubble exits. Stop when liquid reaches the needle tip. Do not push out additional liquid trying to clear a stubborn bubble.

Step 5: Choose your injection site. See the section below on site selection. Clean the chosen area with an alcohol swab and let it dry for 10-15 seconds.

Step 6: Pinch or prepare the skin. For most patients, pinching a fold of skin at the injection site helps ensure you are in the subcutaneous layer rather than muscle. This is especially useful if the site has less fatty tissue.

Step 7: Insert the needle. For most adults, a 90-degree angle (straight in, perpendicular to the skin) works well at the abdomen and thigh. If you have very little subcutaneous fat at the site, use a 45-degree angle to avoid hitting muscle. Insert the full needle length in one smooth motion.

Step 8: Inject slowly. Push the plunger down at a steady, moderate pace. Injecting too fast can increase stinging. You should feel very little resistance.

Step 9: Remove and dispose. Pull the needle straight out in the same angle it went in. Do not recap the needle. Drop it directly into your sharps container. Apply gentle pressure to the site with a clean swab if there is any minor bleeding. Do not rub the site.

Best injection sites

Three primary sites are appropriate for subcutaneous GLP-1 injections. Each has practical advantages depending on your body type and circumstances.

Abdomen

The abdomen (belly area, at least two inches from the navel) is the most commonly used site and the one most patients start with. It has consistently accessible subcutaneous fat, it is easy to see and reach, and you can inject without assistance. Rotate across the abdomen in a clock pattern or grid to avoid using the same spot repeatedly.

Avoid injecting directly into the navel area or into any area with scar tissue, bruising, or skin conditions.

Thigh

The outer and front areas of the thigh (avoiding the inner thigh and the area directly on top of the knee) are another reliable site. The thigh is useful when you want to vary away from the abdomen. Some patients find thigh injections slightly more comfortable; others find them slightly more prone to stinging. The outer thigh tends to work better than the front for most patients.

For a detailed guide to thigh injections specifically for semaglutide, see How to Inject Semaglutide in Thigh.

Upper arm

The back of the upper arm (the tricep area) is a third option, but it typically requires assistance because it is difficult to reach and control the injection angle yourself. If you have someone who can help with your injections, the upper arm is a practical rotation site. It is not recommended for self-injection unless you can reliably reach and stabilize the site.

Rotating sites: why it matters

Repeated injections in the same spot cause the body to lay down scar-like fatty tissue (lipohypertrophy). This thickened tissue absorbs medication more slowly and unpredictably than healthy subcutaneous tissue. Over months of treatment, this can result in inconsistent drug levels even when your dose and technique are the same.

The solution is systematic rotation. Keep a simple log of where you injected each week, or rotate in a clockwise pattern within each site, and alternate between sites on a schedule you can remember.

For specific guidance on choosing the best injection site for tirzepatide, see Best Injection Site for Tirzepatide.

Handling common injection issues

Stinging or burning at the site

The most common cause is cold medication. Allow it to reach room temperature before drawing. A second cause is injecting too quickly. Slow down the plunger push. A third cause is the medication itself. Some patients are more sensitive than others. If stinging is persistent and uncomfortable, contact your care team.

Air bubbles in the vial or syringe

Small air bubbles in the vial are normal and not dangerous. Bubbles in the syringe can usually be removed by tapping the barrel and gently pressing the plunger until the bubble exits. A small bubble that makes it into the injection is not medically significant for subcutaneous injection, but minimizing them is standard practice.

Bruising at the site

Minor bruising after injection is common and typically resolves within a few days. It usually indicates that the needle caught a small blood vessel. Rotating sites reduces the frequency. If you are taking blood thinners or aspirin, bruising may be more noticeable. This is not a reason to stop treatment, but mention it at your next provider check-in.

Medication leaking back out

If liquid appears at the site after you remove the needle, it usually means the needle was not fully inserted or was removed at an angle. Recheck your depth and angle technique. It can also happen if you injected too quickly into an area with limited subcutaneous tissue. Try a different site on your next injection.

Injection site reactions

Redness, minor swelling, or a small bump at the injection site in the first 24-48 hours is common. These are localized inflammatory responses to the needle and typically resolve on their own. If you develop a reaction that spreads, feels warm, or does not resolve within a few days, contact your care team.

For a complete guide to distinguishing normal reactions from those that need attention, see Injection Site Reactions: What Is Normal.

Storing your medication

Before opening: Compounded GLP-1 vials should be stored in the refrigerator (36-46 degrees F / 2-8 degrees C). Do not freeze. Do not store in the door where temperatures fluctuate.

After opening (in-use): Most compounded vials can be stored in the refrigerator for up to 28-30 days after the first use, but check the specific storage instructions that came with your medication. Your pharmacy will indicate the use-by date for your specific vial.

Room temperature use: Vials can typically be kept at room temperature (below 77 degrees F / 25 degrees C) for brief periods, such as the 15-30 minutes before injection. Do not leave medication at room temperature for extended periods.

Travel: Keep your medication in an insulated bag with a cold pack when traveling. Medication that has been above room temperature for extended periods should not be used. When in doubt, contact your pharmacy or care team.

Comparing injectable to oral GLP-1 medications

If you are deciding between an injectable and oral GLP-1 formulation, or if you are considering switching, the practical differences go beyond just the delivery method. Oral semaglutide has specific requirements around timing relative to food and other medications. Its bioavailability varies more between patients. Injectable formulations have more consistent absorption and a longer established clinical record in weight management.

For a detailed side-by-side comparison of oral and injectable semaglutide including how each is dosed, absorbed, and used in practice, see Oral Semaglutide vs Injection.

What’s in this section

This hub covers injection technique and practical guidance for GLP-1 self-injection. The supporting pages go deeper on specific topics:

Best Injection Site for Tirzepatide - Which injection sites work best for tirzepatide specifically, how to choose between abdomen, thigh, and upper arm, and how site selection affects medication absorption.

How to Inject Semaglutide in Thigh - A focused guide to thigh injections for semaglutide, including exact placement, pinch technique, and how to manage sensitivity at this site.

Injection Site Reactions: What Is Normal - A reference guide to common, expected injection site responses and the reactions that warrant contacting your care team.

Oral Semaglutide vs Injection - A practical comparison of oral and injectable semaglutide for patients choosing between the two formats or considering a switch.

For a complete overview of GLP-1 programs including eligibility, pricing, and how to get started, see our GLP-1 Weight Loss guide.