The survey found that around a million sufferers of diabetes could be risking their health and experiencing emotional distress by keeping quiet about their illness.
Of the more than 3,700 people with diabetes polled, it was found that one in three had kept, or were still keeping, their diabetes a secret.
Half of these people said that this had impacted on how they manage their condition and over a third felt this had affected their physical or emotional health.
One of the main reason for not disclosing that they suffered from diabetes was fear of workplace discrimination, the study revealed.
Over half (59 per cent) of those who said they had kept their diabetes secret had not told their employer or colleagues about their condition.
Reasons for doing so included not wanting diabetes to affect employment chances, or people assuming the condition developed as a result of an unhealthy diet.
Barbara Young, chief executive at Diabetes UK, said: “We have to ask why so many people with diabetes keep it a secret.
“There are 2.8 million people diagnosed with diabetes in the UK who need friends, family, employers and the public to understand how common diabetes is becoming and how serious it can be if people aren’t supported to manage their condition.”