He says had his leg there because he was a diabetic, injecting himself with insulin.
Now he's suing.
The 25-year-old says he was taken away in handcuffs while he was injecting himself with life-saving insulin.
Juan Castillo says it takes just 5 seconds to inject himself and he must do it 6 times a day.
"What I did was raise up my leg and massage here where the injection happened so I don't have blood clot," said Castillo.
He says he explained he was diabetic to the Transit Officer but was still taken into custody off the F train. All of this happened in Sept of 2009.
The arrest he actually had no problem with, but what almost killed him he says was having his insulin pen taken away for 30 hours while he was in custody.
"I was throwing up," he said.
After a judge threw the case out he says he had to be in the hospital for three days.
"If you take away insulin, you'll die," said Dr. Daniel Lorber.
Dr.Lorber is an independent diabetes expert. He says if you don't have the insulin, "You are sick as a dog, throwing up, dehydrated and you die within 24 to 48 hours."
And he says what allegedly happened after the subway arrest is not unusual. Other cities' police departments have changed their policies. Eyewitness News did not hear back when we requested comment from the NYPD on this case.
"The NYPD routinely separates people from their meds without paying attention to the consequences," said Mike Lumer, Castillo's attorney.
Castillo's attorney says his client almost died, now needs a new pancreas and that this arrest never should have happened in the first place.
"He should have been left alone on the subway," he said.
Castillo is pursuing this lawsuit saying it's not about the money, it's about changing police policy when it comes to New Yorker's and medication.