Q: Is there a Life Safety Code requirement for cabinet doors to be locked underneath sinks in patient rooms, in a hospital?
A: No… There is no Life Safety Code standard or requirement whereby doors underneath sinks must be locked. However, there is an Infection Control concern that anything stored underneath a sink may become contaminated from soiled water that leaks from the sink drain. Therefore, many accreditation organizations require hospitals to either restrict clean items from being stored underneath sinks, or at least conduct a risk assessment to evaluate the risks associated with that.
As an example, The Joint Commission says in their Frequently Asked Questions that their standards do not specifically address under sink storage, but they say organizations should conduct risk assessments concerning the issue. You need to also contact your state and local authorities to determine if they have more restrictive requirements.
In my travels, I see many hospitals either lock or screw shut the doors to under sink storage. It is an easier way to prevent clean supplies from being inadvertently placed there.