The UK government is creating more places for medical students amid fears a "grade giveaway" could cause a rush for limited university courses.
The additional courses come as universities say they could set their own entrance exams because they can no longer rely on predicted grades.
The results - due next Tuesday in England, Wales and Northern Ireland - could set a new record for top marks.
A report found “grade inflation” could be higher this year than it was in 2020, when for the first time in the history of A-levels the pass rate reached 100 per cent.
Some of the UK’s top universities are already bringing in their own assessments for competitive courses because academics say they can no longer determine the top students.
Schools submit grades for pupils based on a range of evidence, including mini-exams, mock exams and coursework.
Prof Alan Smithers, director of the Centre for Education and Employment Research at the University of Buckingham, the report’s author, said it could be “another bumper year for grades”.
He said several UK institutions were looking to bring in their own assessments, with academics unable to identify top talent because of a “grade giveaway”.
“A lot of students that are perhaps not up to it are getting in and an equal number of talented pupils are being excluded,” he told Sky News.
“We’ve now got inflation in the grades. Universities rely on those grades for making precise decisions about who to admit and who not to.
“At the moment, those A-level grades are not doing that work.”
Last year saw huge controversy after an algorithm caused a downgrading of many pupils’ grades.
The computer-driven model was then replaced by teacher-assessed results.
After the change, schools reported the highest-ever proportion of A* and A grades. Almost two in five A-levels, or 38.5 per cent, were awarded an A* or A last year after the U-turn, up from 25.5 per cent for pupils in 2019.
If more pupils receive high grades, there are fears of a rush for places at sought-after universities and courses. There is also pressure from record numbers applying, with more than 680,000 seeking university places.
Education Secretary Gavin Williamson has promised more courses for medicine due to anticipated high demand.
"Students have worked incredibly hard over the past 18 months and we have continued to put their best interests first to ensure they can progress on to the next stage of their education training or career," he said.
Some UK universities are already reporting oversubscribed interest for medical courses.
Nick Hillman, director of the Higher Education Policy Institute, said it was much harder to create more places in medicine because of the length of the course and cost of training doctors.
He said students may be disappointed if they have to choose medical schools not on their preference list.
"If you've had your sights set on one particular medical school from the moment you applied or even the moment you started your A-levels, it's quite a big mental jump to decide you're going to go somewhere else," he told the BBC.