The test determines whether the pancreas is still producing insulin. It can help diagnose maturity-onset diabetes of the young (MODY). Adults with MODY are often misdiagnosed as having type-1 diabetes and inappropriately started on insulin, the researchers said.
Dr Rachel Besser and colleagues from the Peninsula Medical School in Devon have so far assessed the test in more than 300 patients.
In one trial, the group found the test can be used to show when genetic testing for MODY might be necessary.
Another study, in Diabetic Medicine, showed it was a sensitive and specific method for detecting insulin secretion and might be a practical alternative to standard tests, avoiding the need for hospital investigation.
Dr Besser said the test could replace existing multiple blood tests carried out in hospital.
'It allows patients to produce samples at home and send them via their GP or direct to laboratories for analysis,' she said. 'It is also non-invasive, making it more comfortable for patients, especially children.'
She added: 'Fundamentally, it means that patients will no longer have to attend hospital appointments for blood tests, resulting in greater convenience for them and their GP.'