I sent forms to the DVLA to tell them I had gone on insulin July 20th. I am still waiting to hear. I did e-mail the end of August to enquire on time scales . They replied saying they were behind and waiting for information and would be in touch in due course. You can drive until they tell you cannot, if that is the outcome. You are also obliged to inform your car insurance that you have gone on insulin and are awaiting DVLA response to your driving status. Otherwise, you may not be covered in the event of claim.