The FDA is warning people with diabetes and the public that noninvasive smartwatches or smart rings that do not pierce the skin should not be used to measure blood glucose, according to a press release.

The FDA issued a new safety communication on Feb. 21 to inform people with diabetes that glucose readings taken with smart devices that do not pierce the skin could be inaccurate. Those inaccurate measurements could lead a person to take the wrong dose of insulin or a diabetes medication and precipitate dangerously low glucose levels, which could result in mental confusion, coma or death within hours of the error.

The FDA has not authorized, cleared or approved any noninvasive smartwatch or smart ring for the measurement of glucose. While those devices claim to use noninvasive techniques to measure blood glucose, the FDA said the devices do not test blood glucose directly. The agency said standalone smartwatches or smart rings are different from smartwatch applications that display data from an FDA-approved device that measures blood glucose by piercing the skin, such as a continuous glucose monitoring device. The FDA’s safety communication applies to devices manufactured by dozens of companies and sold under multiple brand names.

Consumers, people with diabetes and their caregivers are advised not to purchase or use smartwatches or smart rings that claim to measure glucose levels on their own. People with diabetes are advised to speak with their health care provider about using an appropriate FDA-approved device. Providers are advised to warn patients about the risks of using unauthorized blood glucose measuring devices and to help patients select an FDA-approved device if needed.