Why did the 21st Century Cures Act change how MDDS is regulated?

The 21st Century Cures Act (2016) amended Section 520(o) of the FD&C Act to exclude most MDDS functions from the statutory definition of a medical device, reflecting a policy judgment that pure data transfer, storage, format conversion, and display functions pose minimal risk and do not need active FDA oversight. Before this amendment, FDA had classified certain MDDS products as Class I devices; after Cures, most MDDS functions fall outside FDA's active regulatory scope entirely.

What is the most common mistake vendors make in claiming MDDS status?

The most common mistake is underestimating how narrowly FDA enforces the boundary between pure data handling and interpretation. Even simple thresholding, trending, or basic derived calculations applied to displayed data typically cross the line into regulated SaMD territory, even though they might feel like modest display enhancements to the development team. Vendors should document their MDDS-versus-SaMD classification logic explicitly and re-run that analysis whenever a feature is added, since a single interpretive feature can reclassify the entire product.

Does MDDS status ever change as a product evolves?

Yes, MDDS classification is tied to specific functions, not to a product as a whole, so adding a new feature that interprets data or triggers a clinical alert can move a previously excluded product into regulated SaMD status even if its original core functions remain unchanged. Manufacturers should version-control feature changes with a documented review step that reassesses MDDS eligibility before each release, rather than assuming an initial classification decision holds indefinitely.

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Software & AISoftware Lifecycle Global MarketsMDDS

Medical Device Data System

Hardware or software intended to transfer, store, convert format, or display medical device data, generally not actively regulated by FDA after 2017 Cures Act amendments.

Reviewed by Christian Espinosa, Founder, Blue Goat CyberLast reviewed June 20, 2026

Definition

A Medical Device Data System (MDDS) is hardware or software intended to transfer, store, convert format, or display medical device data without controlling the functions or parameters of any connected medical device. The 21st Century Cures Act (2016) amended Section 520(o) of the FD&C Act to exclude most MDDS functions from the definition of a medical device, meaning FDA does not actively regulate software whose sole purpose is to perform these functions. However, software that interprets data, generates alarms based on data, or controls another device is not MDDS and remains a medical device.

What the regulation says

FD&C Act §520(o) as amended by the 21st Century Cures Act §3060. FDA's 'Clinical Decision Support Software' guidance (2022, final) and 'Changes to Existing Medical Software Policies Resulting from Section 3060' guidance clarify what remains regulated after Cures.

What this means in practice

MDDS classification has significant strategic implications for software vendors. A platform that purely moves and displays data from connected devices may not require FDA submission; the moment it adds analytics that interpret or trigger clinical action, it becomes a regulated SaMD. The boundary is enforced narrowly by FDA, even simple thresholding or trending logic typically crosses the line. Manufacturers must document MDDS-vs-SaMD classification logic and version-control any feature changes that could move a product across the boundary.

Examples

A hospital's central server collects and stores vital sign measurements from various patient monitors for archival purposes, without performing any analysis or generating alerts.
A smartphone application receives and displays glucose readings from a connected continuous glucose monitor, allowing the user to view their trend over time but not offering interpretive insights or treatment recommendations.
A software module converts data from an infusion pump into a standardized format for integration into an electronic health record system, purely facilitating data exchange without altering device operation or interpreting clinical significance.

Common pitfalls

•Claiming MDDS for software that interprets data, analytics, alarms, scoring, and clinical recommendations are not MDDS.
•Letting MDDS scope creep without re-evaluation, features added over time can shift the product across the regulatory boundary.
•Confusing MDDS with Clinical Decision Support (CDS), they are different exclusions with different criteria under §520(o).

Frequently asked questions

To stay within the MDDS exclusion, software must be limited to transferring, storing, converting the format of, or displaying medical device data without interpreting that data or controlling the functions or parameters of any connected medical device. The moment the software adds interpretive logic, such as generating alarms, flagging abnormal values, or providing analysis intended to inform clinical decisions, it moves outside the MDDS category and becomes a regulated device, typically Software as a Medical Device.

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Category: Software & AI
Acronym: MDDS
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Updated: 6/20/2026

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Hardware or software intended to transfer, store, convert format, or display medical device data, generally not actively regulated by FDA after 2017 Cures Act amendments.

·MDDS classification has significant strategic implications for software vendors.
·The boundary is enforced narrowly by FDA, even simple thresholding or trending logic typically crosses the line.
·However, software that interprets data, generates alarms based on data, or controls another device is not MDDS and remains a medical device.

Remember this

Watch out: Claiming MDDS for software that interprets data, analytics, alarms, scoring, and clinical recommendations are not MDDS.

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