Morning Matthew,
Basically, it depends on your ability to walk. If your Myeloma is affecting you in this way then it goes towards you being eligible for a Blue Badge. Having Myeloma alone is not a blank cheque in getting one. Hope this helps.
Hi Matthew
Give your local authority a ring. After waiting for weeks on a postal application, I rang my local council, gave them the details of my multiple myeloma diagnosis, and received my blue badge within a couple of days. It cost me £5. Worth speaking to them direct. Best of luck.