Device Definition under FD&C Act Section 201(h)

1. Key takeaways

Under United States law, the definition of a medical device is written in FD&C Act section 201(h). The determination follows four steps: whether the article falls within the statutory category words (instrument, apparatus, implement, machine, implant, in vitro reagent, and related items); whether it has a statutory intended use in the diagnosis, cure, mitigation, treatment, or prevention of disease, or in affecting the structure or function of the body; whether it falls within the exclusions, covering uses in animals or other than in humans, or products whose primary intended purpose is achieved through chemical action within or on the body and that are not dependent upon being metabolized; and whether any residual exclusion applies. Running this chain in order, with a written record at each step, converts a definitional question into a repeatable compliance procedure that survives staff turnover and audit scrutiny alike.

• The statutory category words are a parallel list; software is not named in the list but is treated as a device and has its own labeling rule at 21 CFR 801.50.
• The chemical-action exclusion is the boundary between device and drug, and combination products are assigned by FDA through a primary mode of action determination.
• The definition expressly includes components, parts, and accessories, so accessory makers are registration and listing subjects under 21 CFR Part 807.
• Radiation-emitting electronic products attract Subchapter C duties in addition to device duties.
• A four-step determination record is the core deliverable of the first stage of any United States project.

2. Legal basis

The authorities below define what counts as a device and what follows from that status. Where a product sits at the boundary between device, drug, and biological product, FDA’s boundary product guidance and the Office of Combination Products framework provide the operative test, and the result of that test should be documented before registration decisions are made.

3. Expert insights

Insight one: the statutory category words form a parallel list, and software sits outside the list but can be interpreted as an apparatus or machine.

The category words enumerated in FD&C Act section 201(h) are instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, and other similar or related articles. Software is not a separately named word in the list, but FDA regulates it as a device in practice, and specific labeling provisions exist at 21 CFR 801.50 covering software device labeling. This means that a claim of being software rather than a device does not hold under United States law. Development teams that discover the device character of their product late in the cycle typically face retrospective work on labeling, cybersecurity documentation, and quality system records; teams that settle the question at project initiation face none of that, which is why this determination belongs at the very front of the project plan rather than at the end.

Insight two: the exclusion rule for products whose primary intended purpose is achieved through chemical action in or on the body and that are not dependent on metabolism marks the boundary between device and drug.

Where a product achieves its primary intended purposes through chemical action and depends on metabolism for that action, it is ordinarily regulated as a drug; otherwise it is regulated as a device. For combination products, FDA’s Office of Combination Products (OCP) makes the primary mode of action (PMOA) determination, which decides the lead reviewing center. The PMOA determination is therefore not an academic exercise: it routes the dossier, sets the review expectations, and shapes the consultative process between centers. Filing before the determination is made risks the entire submission being redirected, with the associated loss of time and the need to restructure the data presentation around a different center’s expectations.

Insight three: the definition also reaches components, parts, and accessories.

FD&C Act section 201(h) expressly provides that the definition includes any component, part, or accessory. The practical consequence is that an enterprise that sells only accessories to end users also falls within the enumerated subjects of 21 CFR Part 807 and must register and list. Businesses are regularly surprised by this, because an accessory sold on its own looks commercially like an ordinary product line rather than a regulated device activity. The statute, however, follows the product character rather than the commercial arrangement, so accessory catalogs should be swept systematically during scoping, and every item that qualifies should be brought into the registration, listing, and labeling programs from the start.

4. Practical recommendations

• Write the determination as a four-step form with a record kept at each step: category words, intended use, exclusions, and residual exclusions.
• For products containing software, plan the 21 CFR 801.50 labeling requirements and the cybersecurity documentation in parallel from project initiation, not after development is complete.
• For combination products, apply for the PMOA determination first and only then decide which center receives the dossier, avoiding a filing made to the wrong office and a full restart of the process.
• Do not omit accessories and parts from listing, especially accessories sold separately to end users, and sweep the catalog periodically for newly added items.

5. Verification checklist

• □ The four-step determination under FD&C Act section 201(h) has been completed and a written record retained.
• □ It has been determined whether the product contains software; if so, 21 CFR 801.50 labeling has been planned.
• □ It has been determined whether the product is a combination product; if so, a PMOA determination has been planned.
• □ All products sold separately as accessories or components have been enumerated.
• □ It has been determined whether the product is a radiation-emitting electronic product; if so, Subchapter C obligations have been planned.

Regulatory information verified as of October 28, 2026.

How GRZAN can help. GRZAN provides medical device and IVD registration, quality system, US Agent and local testing support for the United States market. Our team manages FDA establishment registration and listing, 510(k)/De Novo/PMA submissions, and supports post-market reporting obligations. Business enquiries: info@grzanglobal.com