Madge McQuire, 84, was 10 minutes early to her physio appointment at Rotorua Hospital last Thursday.
However, after circling the perimeter several times, she found every parking space was occupied.
"That included the disability park, over the road, even along the fence, and the emergency parking that required a special sticker. Not an inch to spare. Other cars were cruising around to no avail," she told the Rotorua Daily Post.
She can only walk small distances, so at short notice, she had no option but to go home without the treatment recommended by a surgeon.
"Who are the people using these parks if the patients have nowhere to go? What can be done about this situation?" she said.
The Lakes District Health Board was "very concerned" by the complaint, and was taking it "very seriously", according to chief operating officer Nick Saville-Wood.
He said it was "very unfortunate and the DHB really regrets this".
"While we have increased the number of disability parks to 21 outside Rotorua Hospital, Lakes DHB still finds that we have logjams for the disabled parks Tuesday to Thursday. Along with the 21 disability parks, we also have a dozen limited stay parks, but again these can all be occupied at peak times which tend to be Tuesdays to Thursdays."
He said staff had been assigned to check the parks.
"If anyone clearly displaying a mobility permit is parked in the limited stay parks for longer than 15 minutes, or in the ED only parks in the main visitor car park, they will not be towed.
"Our staff clearly appreciate that our visitors with a disability can not walk from the general parking areas that are a long distance from the main entrance and so are not likely to hand out warning stickers to cars displaying mobility permits."
Last Thursday 7mm of rain fell, and Saville-Wood said wet weeks tended to put additional pressure on parking.
He said the likelihood of additional parking spaces at the hospital depended on the facility redevelopment plans for mental health services.
"We may have room to extend the parking alongside the current mental health services administration block."
McQuire said she had noticed the parking shortage before, but she had "always found somewhere in the end".
She said she was "perplexed" by the problem.
"There are hundreds of parks. It is about who is using them. The parks close to the entrance should be for patients only, not visitors or staff."
McQuire said the problem was "not anyone's fault".
"I think they [the DHB] are trying but it needs to be sorted."
To help solve parking problems at medical practices, St John Rotorua runs a health shuttle Monday to Friday for appointments from 8am to 3.30pm.
The shuttle collects patients from home half an hour before their medical appointment, then returns them after the appointment.
Rides must be booked 24 hours in advance on 0800 000 606.
There is no charge for the service but a donation is appreciated.