I would say yes, call 999, unless the person who fell insists they are ok, can get up, and absolutely doesn't want you to call. I'm sure that the paramedics would agree.

I have had to call them a few times for a friend this year who had MSA, a rare neurological and terminal illness where degeneration of nerve cells in areas of the brain causes loss of blood pressure control and hence balance, also movement and speech problems among other physical difficulties. He died sadly just two weeks ago, but fortunately in his sleep.

He had several falls, increasing in frequency over the last year, one of the worst getting jammed behind the toilet. I phoned the ambulance but as often occurs in my area there was no-one available and it can take hours for an ambulance to arrive. It was a huge struggle to get him up as it has been on other occasions after a bathroom fall but sometimes I was able to get hold of a stronger male friend to come and help.

Reasons for a fall may not be obvious so medical attention should be sought if in any doubt at all. Once my friend fell and when the ambulance did arrive on that occasion they found his oxygen levels seriously low due to a lung infection / pneumonia. He had to go to hospital for a while and if the paramedics hadn't come that time he may well have not lived for the few extra months that he did.