Mr Neil said the family of John Clark had "clear and justified" concerns about his care at Monklands Hospital, Airdrie.
They had become worried the 77-year-old, who is paralysed down his right side and unable to talk following a stroke, was in danger of dehydration as temperatures rose in his south-facing single hospital room.
Mr Clark's son, Paul, said the window opened only a few centimetres, there was no air conditioning and an electric fan was not allowed, although he saw nurses gathered around a fan at a reception desk.
On four occasions over the course of nine days, Paul Clark said he found his father's bed tray out of his reach, leaving it impossible for him to drink unaided.
Mr Clark also said the emergency cord button was left behind his father on the right, even though he has the use of only his left arm and cannot twist.
Mr Neil, in his role as MSP for Airdrie and Shotts, confirmed he had sought a meeting with the family and the chief executive of NHS Lanarkshire to "seek a guarantee that appropriate procedures are now in place to ensure no patient at the Monklands has to endure this kind of poor service in future".
He said: "I was very disappointed and angry when I heard about Mr Clark's poor treatment in Monklands, especially given all the work the Scottish Government has done with NHS Lanarkshire to improve the quality of service and enhance investment there.
"However, I am pleased the clear and justified concerns Mr Clark raised with me about some aspects of his father's care are being addressed, and that there is a plan to ensure his standard of care is maintained in future.
"I would encourage anyone who has concerns about NHS care to raise them."
Mr Clark said: "We now fear when my father becomes ill because we are genuinely scared of Monklands.
"We fear for my dad in there to the extent I asked the nurse if my father could be sent home as he would receive proper care there.
"We can see what is happening, but it concerns me that people without visitors will go unnoticed and lose their lives to malaise."
Nine days after John Clark was admitted with an impacted bowel - a complication linked to his disabilities - Mr Clark contacted local politicians.
Within hours, he said Mr Neil had arranged a meeting with the health board. Mr Clark's mother, Sadie, later found her husband's room appropriately arranged and the nurses helpful.
Mr Clark, 44, praised the assistance his father has now received but expressed concern about patients who do not have relatives fighting their case.
Monklands Hospital is the focus of a programme to improve patient safety after a rapid review prompted by high mortality rates.
A spokeswoman for NHS Lanarkshire said officials had met Mr Clark and his family to discuss their concerns and were investigating the care his father had received.
She added that some areas of the hospital were "particularly affected" by high temperatures the week before last. "We have now ordered more fans for use throughout the hospital," she said.
"We would always encourage anyone who is unhappy with the care or treatment they have received in NHS Lanarkshire to contact us. We take complaints and concerns seriously and all feedback is shared with staff and used to help develop and improve our services."
Jason Leitch, clinical director of NHS Scotland, has also said the Scottish Government was "very concerned to hear about the issues experienced".
He said an expert group had reported considerable improvements at Monklands this April but there was still more work to be done.