The high "star rating" unregulated health apps can give people a false sense of security does not guarantee medical accuracy or value, and can lead to dire health consequences, researchers have warned.

"People tend to trust user reviews when shopping online and use them to decide which products to purchase, but that doesn't cut it for medical apps," said Timothy Plante, assistant professor at the University of Vermont. For the study published in the journal JAMA Internal Medicine, the team analysed 261 user ratings and reviews of the app "Instant Blood Pressure" downloaded from the Apple iTunes store before being withdrawn from the market in July 2015.

The results showed that the average star rating of the latest version of the app was four out of five stars, and 59 per cent of the reviews assigned the app five stars. Commentary praising the accuracy of the app based on anecdotal experience comprised 42 per cent of the reviews, and 10 per cent of the reviews mention inaccuracy.

They found that 24 reviews claimed to use the app for medical purposes, with 11 people using it to manage their high blood pressure treatments, one person using it to manage kidney disease and another person using it to monitor blood pressure after a heart transplant even after the disclaimer that mentioned that the app shouldn't be used as a medical device and is for "recreational" purposes only.

Six reviews came from people who claimed to be health care professionals including four nurses and one physician who gave an average rating of 4.2 stars out of five. Eleven reviews came from people who said their health care provider -- a total of four physicians and seven nurses -- approved of the app. However only two people said that a nurse and an emergency room physician disapproved of the app, and as a result gave a one-star rating. "Physicians need to be careful; if you're saying you personally use an app, people will trust it," Plante said.