What is the thing called for shots? Understanding Medical Injections

September 27, 2025 •

4 min read

With at least 16 billion injections administered in developing and transitional countries each year, the formal medical term for what is colloquially known as a “shot” is an “injection”. This common procedure involves using a needle and syringe to deliver a liquid medication or substance directly into the body's tissues or bloodstream.

Quick Summary

The proper medical term for a shot is an injection. It is the process of administering a liquid, like a medication or vaccine, into the body using a hypodermic needle and syringe, with the specific technique depending on the substance and its intended effect.

Key Points

Medical Term vs. Colloquialism: The correct medical term for a 'shot' is an 'injection,' which is the procedure of delivering substances into the body with a needle and syringe.
Different Routes, Different Speeds: There are several types of injections, such as intravenous (fastest), intramuscular (fast), and subcutaneous (slow), each designed for a specific purpose and absorption rate.
Essential Equipment: A syringe is used to hold and push the liquid, while a hypodermic needle is the sharp, hollow part that penetrates the skin. Auto-injectors also exist for self-administration.
Site Matters: The location of the injection, whether a muscle, fatty tissue, or vein, is critical for the medication's effectiveness and is chosen by healthcare professionals.
Safety and Procedure: Proper injection technique, including cleaning the site and using sterile equipment, is crucial to prevent infection and ensure the procedure is done correctly.
Applications Beyond Vaccines: Injections are not just for vaccines; they are also used for emergency medications, insulin delivery, and diagnostic tests like TB screening.
Reduced Anxiety: Understanding the process, the equipment, and the different types of injections can help reduce fear and anxiety associated with receiving a shot.

Demystifying Medical Terminology: What is a Medical Injection?

While many people use the term “shot” in everyday conversation, the correct clinical term is an injection. This procedure is a common and essential method of administering medication, vaccines, and fluids. The injection allows a substance to bypass the digestive system, ensuring a more direct and rapid effect. A wide range of medical conditions, from chronic illnesses like diabetes to routine vaccinations, rely on this method of delivery.

The Tools of the Trade: Syringes and Needles

Every injection requires specific equipment designed for precision and safety. The primary tools are the syringe and the needle. The syringe is a pump-like device, typically with a barrel, a plunger, and a tip where the needle attaches. The needle is a hollow, stainless steel tube with a sharp point, and its size can vary based on the injection type and patient size.

Syringe: Holds the liquid medication. Pulling back the plunger draws the substance in, and pushing it forward dispenses it. They come in various sizes, measured in milliliters (mL), and can be either disposable or reusable for specific purposes.
Hypodermic Needle: The needle used for injection. It is available in different gauges (thickness) and lengths. A higher gauge number indicates a thinner needle, which can reduce pain. The length is determined by the injection type and the depth required.
Auto-Injectors: For some medications, such as epinephrine for severe allergic reactions or insulin, auto-injectors are used. These spring-loaded devices are pre-filled with a dose and automatically inject the medication, making self-administration easier and less intimidating.

The Different Types of Injections

Injections are not one-size-fits-all. They are categorized based on where the needle enters the body. The chosen type depends on the medication, the desired speed of absorption, and the clinical purpose. Healthcare professionals are trained to administer the correct type for each situation.

Intramuscular (IM) Injections

Intramuscular injections deliver medication deep into a muscle, which has a rich blood supply for relatively fast absorption. Common sites for IM injections include the deltoid muscle in the upper arm, the vastus lateralis muscle in the thigh, and the ventrogluteal muscle in the hip. Many vaccines, such as the flu shot, are administered this way.

Subcutaneous (SC or SubQ) Injections

Subcutaneous injections are given into the fatty tissue just beneath the skin. This layer has fewer blood vessels than muscle, resulting in a slower, more sustained absorption of the medication. This is ideal for medications like insulin and some blood thinners. Common sites are the abdomen, the front of the thigh, and the back of the upper arm.

Intravenous (IV) Injections

An intravenous injection delivers medication directly into a vein, providing the fastest possible absorption into the bloodstream. In a healthcare setting, this can be done as a quick injection or as an infusion (drip) over a longer period. IVs are used for rapid-acting medications, fluids, and blood transfusions.

Intradermal (ID) Injections

Intradermal injections involve injecting a substance into the dermis, the layer of skin directly below the epidermis. This is the slowest route of absorption and is typically used for diagnostic tests, such as tuberculosis screenings and allergy tests.

How Do Doctors Determine the Right Type of Injection?

The choice of injection type is a careful decision made by a medical professional. Several factors influence this choice:

Desired speed of action: For emergencies, IV is the fastest route, while for long-term, steady delivery, subcutaneous or intramuscular injections are often preferred.
Type of medication: Some drugs are designed to be absorbed slowly, while others require a specific tissue environment to be effective.
Dosage volume: Small volumes might be given intradermally or subcutaneously, while larger volumes of fluid or medication often require an IV.
Patient factors: Age, body mass, and general health can influence the choice of injection site and needle size.

Understanding the Process: What to Expect

While receiving an injection can be intimidating for some, understanding the process can help alleviate anxiety. The procedure is typically quick and involves several key steps:

Preparation: The healthcare provider prepares the medication and selects the appropriate needle and syringe. They will also clean the injection site with an alcohol swab to minimize the risk of infection.
Administration: The needle is inserted at the correct angle for the specific injection type. The medication is then delivered. For most injections, aspiration (pulling back on the plunger to check for blood) is not necessary, especially for vaccines.
Aftercare: After the needle is removed, gentle pressure is applied to the site with a gauze pad or cotton ball. A plaster may be applied. It's best not to rub the area, as this can cause irritation.

Comparison of Common Injection Types


Feature	Intramuscular (IM)	Subcutaneous (SC)	Intravenous (IV)	Intradermal (ID)
Injection Site	Muscle tissue (e.g., deltoid, thigh)	Fatty layer under the skin (e.g., abdomen, back of arm)	Vein (e.g., arm, hand)	Dermis (top layer of skin)
Absorption Rate	Fast	Slow, sustained	Instantaneous	Very slow
Common Use	Most vaccines, antibiotics	Insulin, blood thinners	IV fluids, emergency meds	Tuberculosis and allergy tests
Needle Angle	90°	45°	25° (into vein)	10-15°
Needle Size	Longer, thicker	Shorter, thinner	Varies	Very short, thin

Conclusion: From Shot to Injection

While the word “shot” is a familiar and easy-to-understand term, knowing the proper medical terminology can improve communication and understanding with healthcare providers. The correct name for the procedure is an injection, which is a precise method of delivering medicine with a specific purpose. By understanding the different types of injections and the process involved, individuals can feel more informed and confident during medical procedures. For reliable information on vaccinations and health, always refer to reputable sources like the Centers for Disease Control and Prevention.

Frequently Asked Questions

The medical term for a shot is an 'injection.' A shot is a colloquial term for the medical procedure of injecting a liquid substance, like a medication or vaccine, into the body with a needle and syringe.

There are four main types of injections based on where they are administered: Intravenous (IV) into a vein, Intramuscular (IM) into a muscle, Subcutaneous (SC) into the fatty layer under the skin, and Intradermal (ID) into the dermis layer of the skin.

The primary equipment used for an injection consists of a syringe and a hypodermic needle. The syringe holds the liquid, and the needle is the hollow tube that pierces the skin to deliver the substance.

The injection site is chosen based on the type of injection required. Intramuscular injections, often for vaccines, are given in the arm or thigh, while subcutaneous injections, such as insulin, are often given in the fatty tissue of the abdomen.

The most common form of injection uses a needle, but alternative devices like auto-injectors and jet injectors also exist. These devices can simplify the process, especially for self-administration.

An intravenous (IV) injection is a specific type of injection that goes directly into a vein. While all IVs are injections, not all injections are IVs. Other types go into muscles or under the skin.

Following the correct technique is crucial for safety and effectiveness. It ensures the medication is absorbed properly, minimizes pain and the risk of infection, and prevents potential damage to nerves or blood vessels.

Some injections, like insulin or certain fertility drugs, can be self-administered after receiving proper training and guidance from a healthcare provider. Never attempt to inject yourself or others without professional instruction.