An intravenous (IV) injection is an injection of a medication or another substance into a vein and directly into the bloodstream. It is one of the fastest ways to get a drug into the body, often through a vein in the arm.

IV administration involves a single injection followed by the insertion of a thin tube or catheter into a vein. This allows a healthcare professional to administer multiple doses of medication or medicated infusions without having to re-inject needles to deliver each dose.

This article outlines what healthcare professionals use IV injections for, how IV injections work, and the equipment they require. It also outlines some of the pros and cons of IV injections and infusions, as well as some of their possible risks and side effects.

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IV injections are one of the quickest and most controlled ways to deliver medications or other substances into the body.

A healthcare professional may administer an IV injection in the following situations:

  • when a person needs a potentially life saving medication very quickly
  • when a person needs a very accurate dose of a medication
  • when a person needs a large dose of a medication over an extended period of time
  • when taking a medication by mouth would be impractical or ineffective
  • when a person would otherwise require multiple injections, such as when receiving treatments for some chronic conditions
  • when a person cannot eat or drink and requires fluids through an IV line

The equipment necessary for an IV injection can vary according to several factors, including:

  • the type of medication the person requires
  • whether the person requires the medication rapidly or over an extended period of time
  • how long the person will need the IV for

Depending on the above factors, necessary equipment may include the following:

  • a tourniquet to help the healthcare professional identify a suitable vein
  • local anesthetic to numb the injection site
  • a needle for the initial injection
  • a catheter tube to keep the vein open
  • an access cap that the healthcare professional can open when administering medications and close when not in use
  • a syringe for administering the medication into the catheter
  • IV bags and lines for delivering infusions
  • gauze, bandage, and medical tape to help protect the injection site
  • imaging machines, such as X-ray or ultrasound machines, to ensure that a central line is in place

A healthcare professional may deliver IV drugs or other substances through a peripheral line or a central line. The sections below look at each of these in more detail.

Peripheral line

A peripheral line, or a peripheral venous catheter, is a common form of IV injection that is suitable for short-term treatment.

When placing a peripheral IV line, a healthcare professional will:

  1. Inject a needle into the person’s vein.
  2. Push a small plastic catheter over the needle and into the vein.
  3. Remove the needle, leaving the catheter in place.
  4. Place an access cap over the catheter, which allows them to administer medications without having to re-inject a needle.

A peripheral line may be useful for both rapid injections and time-based infusions. The following sections look at each of these in more detail.

Rapid IV injections

These involve inserting a dose of a drug directly into the person’s bloodstream. Healthcare professionals may also refer to a rapid injection as a push or a bolus.

Time-based IV infusions

These involve delivering a medication into a person’s bloodstream gradually over time. This method involves administering medications through an IV line attached to a catheter. There are two main delivery methods for IV infusions: drip infusions and pump infusions.

Drip infusions use gravity to deliver a steady supply of the infusion over time. With drip infusions, the healthcare professional must suspend an IV bag above the person receiving treatment, thereby ensuring that gravity draws the infusion down through the line and into the vein.

Pump infusions involve attaching a pump to the infusion. The pump delivers the infusion into the person’s bloodstream in a steady and controlled manner.

Central lines

A central line, or a central venous catheter, accesses a more central vein within the torso, such as the vena cava. The vena cava is a large vein that carries blood back to the heart. Healthcare professionals use X-rays to determine the ideal placement of the line.

There are four types of central line:

  • Percutaneous central venous catheter: A healthcare professional inserts the catheter directly through the skin to reach the internal or external jugular, subclavian vein, or femoral vein.
  • Peripherally inserted central catheter (PICC): A PICC line involves inserting a catheter from a peripheral vein on the outer body and carefully feeding it toward the heart.
  • Tunneled line: A tunneled line involves inserting a needle under the skin and feeding it a significant distance before penetrating the central vein.
  • Port: A port is a small reservoir covered in silicone. A healthcare professional implants the port under the skin of the arm or chest, where it feeds into the central vein. They then inject each dose of the medication through the skin and into the reservoir.

Some common sites for short-term IV lines include forearm locations, such as the wrist or elbow, or the back of the hand. Some situations may require using the outer surface of the foot.

In very urgent situations, healthcare professionals may decide to use other injection sites, such as a vein in the neck.

Central lines generally feed into the superior vena cava. However, the initial injection site will typically be in the chest or arm.

The sections below look at some pros and cons of direct IV injections and infusions.

Direct IV injections

A direct IV injection, or IV push, involves injecting a therapeutic dose of a medication or another substance directly into a vein.

The benefit of a direct IV injection is that it delivers the necessary dose of a drug very quickly, which helps it take effect as rapidly as possible.

The drawback of a direct IV injection is that receiving larger doses of a medication may increase the risk of sustaining damage to the vein. This risk may be higher if the drug is a known irritant.

A direct IV injection also does not allow a healthcare professional to deliver a large dose of a drug over an extended period of time.


An IV infusion involves delivering medical infusions through an IV line attached to a catheter.

The benefits of an IV infusion include:

  • being able to control the dose and delivery speed
  • being able to deliver larger doses over time
  • ensuring that the drug remains in the system over a longer period of time

The drawback of an IV infusion is that it does not allow for a large dose of a medication to enter the body at once. This means that the therapeutic effects of the drug may take time to appear. For this reason, an IV infusion may not be an appropriate method when a person requires a medication urgently.

Risks and side effects from IV injections are not uncommon. It is an invasive procedure, and the veins are delicate.

One 2018 study notes that up to 50% of peripheral IV catheter procedures fail. Central lines may also pose problems.

The following sections outline some potential risks and side effects associated with IV injections.


One of the most common complications of IV injections is inflammation of the vein, or phlebitis.

Research in The Journal of Vascular Access notes that phlebitis occurs in up to 31% of people using IV catheters during infusions. The symptoms are typically manageable, with only about 4% of all people developing severe symptoms.

Drug irritation

Direct injection of a drug into a peripheral vein can cause irritation and inflammation in surrounding tissues. This irritation can be due to the pH of the drug or other irritating ingredients that the drug may contain.

Some possible symptoms of drug irritation include swelling, flushing or discoloration, and pain at the injection site.


Sustaining damage to a vein may cause blood to leak out of the vein, resulting in bruising at the injection site.

Drug extravasation

Drug extravasation is the medical term for when an injected medication leaks out of a blood vessel and infuses into surrounding tissues. This can cause symptoms such as:

  • pain
  • tissue damage or necrosis
  • scarring


In some cases, bacteria from the surface of the skin may get into the catheter line and cause an infection.

Central line issues

Central lines typically do not carry the same risks as peripheral lines, though they do carry some risks. Some potential risks of central lines include:

Central lines may also stop working or start to come out.

If a person suspects that there may be a complication with their central line, they should notify a doctor as soon as possible.

IV injections are quick, controlled ways to deliver medications directly into the bloodstream.

The type and method of IV injection a person requires will depend on several factors. These include the medication and dose they require, how urgently they require the medication, and how long the medication needs to remain in their system.

IV injections do pose some risks, such as pain, irritation, and bruising. More severe risks include infections and blood clots.

If possible, a person should discuss the potential risks and complications of IV injections with a doctor before receiving treatment in this way.