A new wearable device can tell how much its owner has had to drink, how tired they are and more – all while fitting into a tiny circle on their arm.

The new device, created by engineers at the University of California San Diego, can continuously monitor a variety of health metrics with its owner barely aware it is there.

It can track glucose, alcohol and blood levels, all together and at the same time.

Such technologies do already exist, but they are unwieldy. Continuous glucose monitors can examine people’s blood sugar, for instance, but only that; blood lactate tends to be measured by extracting people’s blood during exercise.

Instead, the new device works as a “complete lab on the skin” said Joseph Wang, one of the authors of the new research, and so can allow scientists to examine a variety of things at once and look for how they relate to each other. “It is capable of continuously measuring multiple biomarkers at the same time, allowing users to monitor their health and wellness as they perform their daily activities,” he said.

The small device is the size of a stack of small coins and sticks onto the skin with a patch of tiny needles, each of which are about a fifth of the width of a human hair. Those needles penetrate very lightly into the skin and sense molecules in the fluid around the cells, scientists say.

It uses those sensors to gather information on what is happening to people’s bodies and send that to a smartphone app, the researchers say.

When it is finished with, the micro needle patch can be taken out and thrown away. It can then be swapped over in the reusable electronic case, which in turn can be charged up.

Researchers tested the equipment on five people, who exercised, ate a meal and drank wine. Scientists then took measurements of their blood glucose, alcohol levels and blood lactate, and compared them with traditional equipment for doing so.

The research is described in a new paper, ‘An integrated wearable microneedle array for the continuous monitoring of multiple biomarkers in interstitial fluid’, published in the journal Nature Biomedical Engineering.