A new type of  ‘nano ink’, embedded under the skin, could act as a blood glucose ‘early warning system’ for diabetics.

More importantly for patients, it could also mean an end to painful, invasive blood testing by the traditional method, using lancets to draw blood samples which are subsequently analysed by a portable electronic meter.

The glucose ‘mood tattoos’ couldn’t be simpler to use. When the nano-ink shows orange, your glucose level is normal. When it turns yellow, the level is too high. And, when the tattoo turns purple, your glucose is too low.

Researchers say the telltale tattoo need not be large or obvious. A patch just a few milimetres across would suffice.

Researcher Heather Clark of Draper Laboratory in Cambridge, MA, says the tattoo would require a small infrared light source to view the varicoloured fluorescence of the patch. But that would be a great improvement over existing systems which, as well as being invasive, require constant replenishment of consumable supplies.

The blood glucose testing tattoo is currently in a very early stage of testing. No word from Draper Labs when an actual product could be available to diabetes sufferers.