What is a Medical Device?
The statutory definition
Under Section 201(h) of the Federal Food, Drug, and Cosmetic Act (FD&C Act), a medical device is defined as:
an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory which is:
- recognized in the official National Formulary, or the United States Pharmacopeia, or any supplement to them,
- intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or
- intended to affect the structure or any function of the body of man or other animals, and which does not achieve its primary intended purposes through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of its primary intended purposes.
The full definition appears at 21 U.S.C. § 321(h).
The intended use test
The most important element of the definition is intended use — what the manufacturer intends the device to be used for, as expressed in:
- labelling (label and package insert);
- promotional materials and advertising;
- instructions for use (IFU); and
- statements made by the manufacturer or its representatives.
This means the same physical product may or may not be a medical device depending on how the manufacturer presents it. A glucose meter sold for diabetes monitoring is a medical device; an identical meter sold as a "wellness tool" with no diagnostic claims may not be — but FDA evaluates these situations carefully.
FDA's intended use analysis is distinct from the EU's "intended purpose" framework and Australia's TGA framework. In the US, labelling and promotional claims drive the analysis, and FDA can take enforcement action if off-label promotion creates an implied intended use.
Common examples by category
| Category | Examples |
|---|---|
| Diagnostic imaging | MRI, CT scanners, X-ray equipment, ultrasound |
| In vitro diagnostics | Blood glucose meters, pregnancy tests, COVID-19 antigen tests |
| Therapeutic devices | Pacemakers, defibrillators, infusion pumps, ventilators |
| Surgical instruments | Scalpels, retractors, electrosurgical units |
| Implants | Hip and knee replacements, stents, cochlear implants |
| Software (SaMD) | AI-powered diagnostic software, clinical decision support |
| Dressings & bandages | Wound dressings, surgical drapes (with medical claims) |
The "chemical action" exclusion
Critically, the definition excludes articles that achieve their primary intended purpose through chemical action within or on the body. This is the dividing line between a device and a drug:
- A drug achieves its effect chemically or metabolically (e.g., aspirin, antibiotics).
- A device achieves its effect mechanically, electrically, thermally, or through other non-chemical means.
Combination products — articles that combine drug, device, and/or biologic components — are handled under a separate framework (see Combination Products — 21 CFR Part 3).