When your doctor prescribes a liquid medication, you might receive it by injection or infusion. While both methods deliver the drug directly into the body without using your digestive system, they work differently.
Here is what you need to know about the differences between infusions and injections.
An injection — often called a “shot” — uses an auto-injector pen or a syringe and a needle to push a dose of medication quickly into your body. Injections are usually completed in a matter of seconds.
There are three main types of medical injections:
- Subcutaneous: The medication goes into the fatty layer of tissue just under the skin. Examples of medications delivered via subcutaneous injections include GLP-1 medications, insulin, and certain allergy medications.
- Intramuscular (IM): The needle goes deeper, directly into a muscle. This is how most injected vaccines, like the flu shot, are given.
- Intravenous (IV): The medication is injected straight into a vein for immediate use by the body.
An infusion is a method of delivering medication slowly over a longer period. Instead of a quick shot, the medication drips through a tube attached to a needle or a small plastic tube (catheter) placed in your body.
Infusions are used when a medication needs to enter your bloodstream at a controlled, steady pace.
- How it is given: Most infusions are intravenous (IV), meaning they enter a vein, but some can be given just under the skin (subcutaneous infusions).
- Timeframe: An infusion can take anywhere from 30 minutes to several hours.
- Location: Because they take time and require specialized equipment, such as an IV pump, infusions are usually performed in a hospital, a specialized infusion center, or a doctor’s office or clinic by a healthcare professional.
The main differences between these injections and infusions come down to time, amount, and equipment.
| Feature | Injection (“shot”) | Infusion (“IV drip”) |
| Time | Done in seconds | Takes 30 minutes to several hours |
| Amount of Medicine | Small amounts (usually a few milliliters) | An auto-injector pen or a needle and a syringe |
| How it Flows | Large amounts of fluid or medication | Drips slowly using gravity or an electronic pump |
| Equipment | An auto-injector pen, or a needle and a syringe | Needle, IV bag(s), long tubing, and poles or pumps |
Your doctor decides on an injection or an infusion based on the specific drug prescribed and your medical needs:
- Why choose an injection? Injections are ideal for quick treatments, small doses, and routine medications such as vitamins or vaccines. Many injections can also be safely administered at home by patients.
- Why choose an infusion? Infusions are necessary when a drug is too strong to be given all at once, or when a patient needs a large volume of fluids, chemotherapy, or specialized biologic medications.
Both methods are highly effective ways to ensure your body receives the exact amount of medication your doctor prescribes.
Disclaimer: While Medical News Today strives for factual, comprehensive, and current drug information, this article is not a substitute for a licensed healthcare professional’s expertise. Always consult a doctor before taking or discontinuing any medication. Drug information is subject to change and may not cover all uses, directions, precautions, warnings, interactions, reactions, or adverse effects. The lack of a warning does not guarantee a drug’s safety, effectiveness, or appropriateness for all patients or specific uses. Learn more about our approach to content integrity.