St John Ambulance staff have dealt with a steady stream of patients this morning and people are now beginning to be treated for dehydration.
One person has been taken to hospital with abdominal pain.
St John Ambulance special events manager Charlotte Guscott said so far it has been "the expected".
"The blisters are out in force with people wearing new footwear to the Big Day Out, There's been lots of band aids and tampons being handed out," Ms Guscott said.
"There's also quite a bit of alcohol intoxication. There's not a lot we can do except administer fluids - give them water - and put a line in to get some fluids into them."
St John have stations around the ground and mobile doctors and ambulance staff are travelling around on golf carts and segways.
A full medical clinic is also on site to deal with "everything and anything", Ms Guscott said.
"Last year we saw 1100 people and we're expecting the same sort of number," Ms Guscott said.
Two people have been arrested for trespassing, but police say the crowd is generally well behaved.
Inspector Derek Davison said there have been more arrests since this morning but he could not say how many.
"They're not significant offences. We've got a fresh group of police now on site."
He said the event is well managed and the number of arrests made each year is steadily declining.
"When it first started there were about 120 to 130 arrests but now the serious crime has all but disappeared," Mr Davison said.
He said today's arrests were likely to be in the single figures.
Mr Davison said more than 80 police officers were patrolling inside and outside the ground.