I recently had to call out a paramedic. I had been tired and a bit breathless and generally unwell for several days and then developed other more concerning symptoms (didn't have co-vid19 as no cough or temperature). My call to 111 service for advice resulted in the arrival of an ambulance.
When the paramedic was taking my medical history and listing my medications he said I was also iron deficient as B12 injections meant I was lacking in iron. I refrained from saying anything but was concerned about his lack of understanding but then again doctors don't know about B12 deficiency either.