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BLOG: SNOMED International seeks community feedback on proposed description character limit increase

May 8, 2024

When SNOMED International prepares to make changes to various aspects of SNOMED CT, most of which are driven by Member and user request, we often ask our community for their feedback on the potential impact to them.

We are now launching a community consultation to solicit feedback on a proposal to increase the size limits of SNOMED CT concept descriptions to 4096 from the current limit of 255 characters. While this change does not represent a modification of the existing specification, it could be disruptive to implementers who have coded fixed length limits into their systems.

In this Q&A, SNOMED International Technical Specialist Peter Groves Williams explains the proposed change, its potential benefits, the feedback process and timelines, and the issues that may need to be considered in such an update.

Q: What are we asking the community to provide feedback on and why?

A: We are considering increasing the maximum length of Fully Specified Name (FSN) and Synonym descriptions from the current limit of 255 to its maximum of 4096 characters, representing the largest number of characters allowed by the specification. We want to understand how this will affect implementers as it may have an impact on software vendors who have created data storage structures that are not dynamically sized. It is important for SNOMED International to understand how this change will affect them, and how we can support them.

Q: Why are we considering this change?

A: This increase is primarily to accommodate medicinal product FSNs, as their formation is procedurally dictated by the concept model. Terming guidance leads to the current limit being exceeded where there is a large number of ingredients, which is particularly common in multivalent vaccines. Increasing the limit to 4096 characters will ensure that SNOMED CT has the  flexibility to accommodate future terming requirements. 

Q: When does the consultation period start and end?

A: The consultation is open now and runs until July 31, 2024.

Q: Are there any potential downsides or risks to this change?

A: That is the purpose of the consultation – to understand how the proposed change might impact specific implementers so we can help ensure an easy transition in a feasible time frame.

Q: What does this mean to me?

A: SNOMED CT users should check with their software provider to ensure that relevant storage systems are capable of handling longer descriptions; that they either do not feature a 255 character limit, or that this limit can be increased prior to loading in a release of SNOMED CT which features longer descriptions. The actual timing of that release will be determined in response to feedback received from this consultation exercise.

Q: How can I learn more and provide feedback?

A: Visit this page for all the details and background and for the link to the feedback document.

Questions? Email us at

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