Kiwi medical students face "astonishingly high" debts and some will be unable to finish their studies because of limits placed on how many years they can apply for study loans, a lobby group says.

A study in the New Zealand Medical Journal has found about 28 percent of Kiwi medical graduates finish up with more than $90,000 of debt - a massive increase from a decade ago.

New Zealand Medical Students' Association says the problem occurs because medical degrees are expensive, at just over $15,000 a year in course fees, plus estimated average living costs of another $10,000.

On top of this, postgraduate students are only able to apply for loans to cover fees for eight years of university studies.

This means those who complete a separate degree before starting their medical studies often face a year or two at the end of their medical degree where they cannot apply for a student loan.

Association president Kieran Bunn said it was an "abysmal state of affairs" with the lobby aware of 30 students presently unable to apply for student loans for their final year of medicine.

"We desperately need doctors with a wide set of skills and from a wide variety of backgrounds to tackle the challenges of our future health system," he said.

Students unable to apply for a study loan will need to find approximately $25,000 a year without any government support, the association said.

"As the course is full time, there is little to no opportunity to work while studying," NZMA said.

"As well as the remarkable waste of talent we suffer by preventing medical students from finishing their degrees, the limit also risks closing the door to medicine on those who don't come from wealthy backgrounds," Mr Bunn said.