The Court of Appeal will consider if a patient's personal circumstances should influence the NHS when it decides whether to fund treatment.
Thomas Condliff, who weighs 22 stone (140kg) and has type 2 diabetes, is challenging a decision to refuse him a gastric bypass operation.
NHS North Staffordshire says he does not meet its criteria for weight loss surgery.
Decisions about exceptional funding are based on medical factors alone.
Mr Condliff, 62, was initially refused funding for a gastric bypass operation because his weight/height ratio (Body Mass Index) fell below the threshold set by his local primary care trust.
At 22 stone his Body Mass Index (BMI) is about 43, but in North Staffordshire only patients with a BMI over 50 are routinely treated with weight loss surgery. A decision to refuse him funding as an exceptional case was upheld in an earlier court hearing.
Now Mr Condliff is taking his legal battle to the Court of Appeal in a case that has implications for many other areas.
NHS North Staffordshire makes its decisions for exceptional funding on the medical condition of the patient, and rules out considering their personal circumstances.
Prisoner at home
As a result of his diabetes Tom Condliff has lost the sight in one eye, and he also has kidney problems. He can no longer stand or walk for more than a short time and relies on his wife, Lana, to help him wash and dress.
He says that during his legal battle his quality of life has worsened, and even an extremely calorie-restricted diet has failed to help him lose weight.
"I've been given about a year to live by one of the specialists. I feel more and more poorly each day, my diabetes is way out of control."
Having failed to overturn the initial decision to refuse a gastric bypass, he is now resting his hopes on asking the courts to compel the NHS to take into account the impact on his life and that of his family.
"My wife barely goes out, because she doesn't want to leave me. It's awful just being locked indoors. It doesn't matter where you live, how nice it is, it's still a cage. "
Human rights challenge
In the two-day hearing, the Court of Appeal will hear evidence from both sides on whether Article 8 of the Human Rights Act should be applied to how the NHS makes decisions on funding. It sets out the broad right to a family life.
In common with many other primary care trusts, North Staffordshire has a policy of only considering medical evidence when it makes decisions about exceptional funding. The trust says it is part of a commitment to deal with all patients in a fair and even handed manner.
In order to be granted exceptional funding a patient has to show he would have a greater than average medical benefit from any treatment.
If Mr Condliff was successful, the PCT would have to look again at his case, but could still reach the same decision. It might also open the door to further legal challenges.
Although this will not be considered by the court the case also highlights the variation in funding for weight loss surgery.
The guidelines for the NHS in England and Wales suggest patients should be considered if they have a BMI of over 40, or lower if they have other serious medical conditions.
The Royal College of Surgeons has argued that many patients who meet those criteria and could benefit from an operation are turned down at local level for NHS treatment.
Judgement in Mr Condliff's case is set to be reserved until a later date.