Whenever working around horses, we all know it is best to avoid loud noises and fast movements that might startle them – that’s common sense. This is especially important when giving injections because you are about to poke them with a sharp object and you want to avoid any negative associations when managing the health care of your horse. Always have a lead rope and halter on hand with someone holding the horse for you when giving any injection. Do not wrap the halter rope around your hand or arm to avoid being dragged if the horse runs.

There are three different routes of injections you might need to give, either for best health management practices for equine health, as a treatment or in emergency situations. They are intravenous (IV), intramuscular (IM), and subcutaneous (Sub-q). In more common terms: in the vein, in the muscle or under the skin.

It is rare for most horse owners to give IV injections; these are most likely done by the veterinarian. If you are required to give an IV injection or draw blood, your veterinarian will instruct you on the best procedure to do so.

There are three locations on the horse where IM injections would be appropriate, depending on volume of injection. The cervical muscle, which is a triangular area formed by the cervical vertebra, the front edge of the scapula and the neck ligament (IMAGE A), is for volumes of less that 15 ml for a single location. Another is the pectoral muscle, the muscle between the front legs (IMAGE A), which can be used for volumes greater than 20 ml for a single location. Lastly is the rump area on either side of the tail, from below the tuber ischia (lower protuberance of the pelvis) to where the muscle joins the tendons (IMAGE B), which can also be used for volumes greater than 20 ml. Ideally, we don’t want to give more than 15 ml in any single IM injection spot as large volumes can increase pain and swelling at the injection site.

Always follow the label directions for the recommended location for that specific vaccine or medication as well as the required size needle and syringe. Never change what is recommended on the label unless specifically instructed to do so by your veterinarian. For both IM and Sub-q injections, you should clean the injection site with an alcohol pad until dirt is removed before inserting the needle.

Needle Know-How
Needles are measured in gauges. The larger the gauge, the thinner the needle.

For IM injections, you can either pinch the skin next to where you insert the needle or tap firmly with your finger before inserting. This helps prepare the horse that something is coming so they don’t jump away from you. You should insert the needle through the skin up to the hub and aspirate (pull back syringe plunger) to ensure you didn’t inadvertently puncture a vein in the process. If you see blood, redirect the needle and aspirate again. Once you aspirate cleanly, you can inject the medication or vaccine and remove the needle. If you have to give a volume higher than that one location can hold, rotate to another until you’ve given the total volume recommended so you don’t injure the muscle.

For Sub-q injections, shorter needles are typically used and the label recommendations will tell you. Insert the needle at a slight angle ¼ to ½ inch and aspirate to ensure you haven’t punctured a vein. If you get blood into your syringe, redirect the needle and aspirate again. Once you aspirate cleanly, you can inject the vaccine or medication. While doing so, place a finger over the injection site, you should feel a slight “bubble” form. Remove the needle once the injection is completed. This “bubble” will decrease as the liquid is slowly absorbed by the body. There are some potential side effects to watch for when giving any sort of injection – abscess, muscle soreness and swelling at the injection site. Severe cases will require you contact your local veterinarian for recommended treatments.

Brenda Jackson, Murray County Extension Coordinator & Agriculture and Natural Resources Agent