The FDA has issued a warning on Wednesday that it has blessed any smartwatch or smart ring that claims to measure blood glucose levels. The use of these dodgy devices can lead to wrong measurements and blunders in managing diabetes that can be deadly, the agency said.

These dodgy devices are different from smartwatch apps that show data from FDA-approved continuous glucose monitoring devices that pierce the skin.

The FDA did not name and shame any brands but said the sellers of these dodgy smartwatches and smart rings advertise using non-invasive techniques to measure blood glucose without requiring people to prick their fingers or pierce their skin.

However, the agency said these devices do not directly test blood glucose levels, urging punters to steer clear of buying them for that purpose.

The agency also advised health care providers to chat with their patients about the risk of using dodgy blood glucose measuring devices and to help them pick a proper authorised device for their needs.

The agency is working to make sure that manufacturers, distributors, and sellers do not flog dodgy smartwatches or smart rings that claim to measure blood glucose levels, the FDA said in the statement.

"If your medical care depends on accurate blood glucose measurements, talk to your health care provider about a proper FDA-authorised device for your needs."

The FDA's warning comes as more people turn to smartwatches and smart rings to monitor their health and fitness. Some of these gadgets claim to measure blood pressure, heart rate, oxygen levels, and even stress levels.