Pensioner Claude Bradshaw, of Parkfield Road, was refused a blood test at the Community Hospital on Monday because too many patients turned up.
"I was told by a nurse that the doctors had sent too many people for a blood test," he said.
"I am reasonably mobile so I went to Macclesfield, but a lot of elderly people couldn't."
The clinic at the Bexton Road centre closed 30 minutes early because the nurses were fully booked. Yesterday (Tuesday), a spokesman for the NHS Trust apologised and described it as an 'exceptionally busy morning.'
He said the clinic had been forced to close early because so many samples needed testing.
"The patients are referred to the hospital by their GPs so the numbers vary," he said.
"The blood samples have got to be returned to the lab within a limited time so we couldn't extend the clinic because they would not have been analysed properly."
Mr Bradshaw, 66, suffers from a heart condition that requires regular blood checks.
But on Monday, he arrived at the clinic at 10.50am to be told there were no more tests available.
He has now organised a meeting with Tatton MP Martin Bell to discuss problems with the NHS.
Yesterday, the hospital spokesman assured Knutsford residents that the service, which is provided on Mondays and Thursdays, was not being cut.
"We would urge patients to get there as early as possible so they know they will be done that day," he said.
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