Version July 2025
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What are anticoagulants? —
These are prescription medicines that prevent or treat blood clots. They are also known as "anti-clotting medicines." People sometimes call them "blood thinners," but they do not actually thin the blood.
Medicines to prevent or treat blood clots come in different forms. Some come as pills. Others are given as a shot or through a thin tube that goes into a vein, called an "IV."
These instructions are for how to give an anticoagulant shot. Examples of anticoagulants that come as a shot include:
●"Unfractionated" heparin
●"Low molecular weight" heparin such as enoxaparin (brand name: Lovenox)
●Fondaparinux (brand name: Arixtra)
Your doctor or nurse will tell you when and how often to give yourself the shots. Try to do it at the same time (or times) each day. They will also talk to you about what problems to watch for and when to call for advice.
How do I give the shot? —
Below are the general steps.
Decide where you will give the shot:
●The shot is usually given in the belly area, but some people use an arm or leg. Do not use the exact same spot twice in a row, but a spot nearby is OK. Switching sides of the body is a good way to make sure you do not use the same spot twice in a row. This helps prevent soreness and bruising. It might help to keep a record of where you give the shot each time.
●Do not give the shot in a spot that is very close to a mole, scar, wound, or rash.
●Give the shot at least 2 inches (5 cm) away from your belly button.
●If you are pregnant, talk to your doctor or nurse. They might tell you to use a different spot than the belly area after a certain point in your pregnancy.
Prepare yourself and your supplies:
●Wash and dry your hands.
●Get your medicine, syringe, and an alcohol wipe.
●Check to make sure you have the right medicine and it has been stored correctly. It should be stored at room temperature, away from light and moisture. Check the date to make sure it is not expired.
Get the syringe ready:
●If you are using a prefilled syringe, you do not need to do anything to get it ready. Check the liquid in the syringe:
•The liquid should be clear and colorless or pale yellow. If it looks cloudy or discolored, do not use it.
•If you see an air bubble in a prefilled syringe, this is OK. Do not try to remove the air bubble. It helps to make sure you get all the medicine when you give the shot.
●If you need to fill the syringe (figure 1):
•Take the cap off the bottle (vial) if it is new.
•Gently roll the bottle between your hands, or turn it upside down a few times, but do not shake it. Shaking can damage the medicine.
•Clean the top of the bottle with an alcohol pad. Let it air dry.
•Pull the plunger back until the tip is at the line showing the dose of medicine you need. This fills the syringe with air.
•Remove the cap from the needle. Do not let the needle touch anything that has not been cleaned with alcohol, such as your bare hand, a table, or a piece of cloth or paper. If the needle does touch something by accident, do not use it.
•Holding the syringe, push the needle into the rubber stopper on the bottle. Then, push the plunger so the air goes into the bottle.
•Turn the bottle with the syringe in it upside down, and hold the bottle with 1 hand. Make sure the tip of the needle is in the liquid. Pull back slowly on the plunger with your other hand to put the medicine into the syringe. If you pull back too fast, it can cause air bubbles. Do this until the medicine reaches the line for the dose you need.
•Look at the medicine in the syringe. If you see any air bubbles, push the medicine back into the bottle and repeat the above step to fill the syringe. Repeat this until you do not see any air bubbles in the syringe. You can also gently tap the syringe to move the air bubbles toward the needle.
•Turn the bottle upright, and pull the syringe with the needle straight out of the bottle. Check the syringe to make sure you have the right dose.
Give the shot (figure 2):
●Sit down in a comfortable position. It might help to hold an ice pack on your skin for a few minutes before you give the shot.
●Clean the skin where you will give the shot with an alcohol wipe. Let the skin air dry for a few seconds.
●The shot should go under the skin, but not into the muscle. Try to relax the muscles near where you will give the shot.
●Pinch 1 to 2 inches (2.5 to 5 cm) of skin between your fingers and thumb on 1 hand.
●Hold the syringe at a 90° angle to the skin. Push the needle all the way into the skin you are pinching.
●Slowly press the plunger all the way down.
●You might feel some discomfort and burning when the medicine is going in. Once all the medicine is in, wait a few seconds and then remove the needle at the same 90° angle. Then, stop pinching the skin.
●Gently press on the area where you gave the shot. Do not rub or massage it, as this could lead to bruising. If there is a little bleeding, you can cover it with a bandage. If needed, use gauze or a cotton ball and put slight pressure on the area.
●Do not try to put the cap back on the needle. Some types of syringes have a shield that covers the needle. Throw the used needle away in a special container called a "sharps container" (picture 1). Your doctor or nurse might give you one. If not, you can use a very thick plastic container such as a laundry detergent bottle.
●Put your supplies away.
●Return the bottle of medicine to wherever you normally store it. Make sure you know where and how to store your medicine when you're not using it. It should be kept at room temperature.
What else should I know? —
Your doctor or nurse will tell you about any problems to watch for, and when to call for advice. They will want you to call if you have any unusual bleeding or bruising.
Your doctor or nurse will also tell you if you need to have follow-up blood tests.
Patient education: Deep vein thrombosis (blood clot in the leg) (The Basics)
Patient education: Deep vein thrombosis (blood clot in the arm) (The Basics)
Patient education: Pulmonary embolism (blood clot in the lung) (The Basics)
Patient education: Prosthetic valves (The Basics)
Patient education: Factor V Leiden (The Basics)
Patient education: Deep vein thrombosis (DVT) (Beyond the Basics)
Patient education: Pulmonary embolism (Beyond the Basics)
