Use of these units was due to cease on 1 June as the UK switched to exclusive use of mmol/mol units, but this change has been delayed.
Dual reporting of percentage units alongside mmol/mol units will continue until October.
GPs have warned that clinicians and patients are not yet familiar with the new units and academic journals have said they would continue using the old units.
Diabetes UK said the change was because clinicians and biochemists had 'expressed concern that the new measurement numbers are still not widely used or understood'.
Simon O'Neill, director of care and policy at Diabetes UK, said: 'It is regrettable that we have had to postpone this change but it is clear that the new numbers are not widely understood yet and making the change now could cause confusion for clinicians and patients.
'This is a one-off delay, so it is important that we work hard to get the new numbers understood before the new cut off date on 1 October this year.'