Brisbane Broncos forward Corey Jensen has revealed more frightening details behind the health scare that landed him in the hospital for nine days.

From the moment of diagnosis of a pulmonary embolism at the end of April, Jensen was given a 12-week stint at minimum.

In April, it was reported he had shed roughly 10 kilograms since the ordeal began, which on Thursday afternoon when speaking to the media, he confirmed was the case, and fluid was drained from his lungs during his hospital stay.

Jensen has been placed on blood thinners, and the Broncos' medical staff are in no rush to clear him for contact.

The 32-year-old revealed that a couple of weeks leading into the Tigers game back in Round 7 at Campbelltown Sports Stadium, he started suffering cold and flu symptoms.

By the week of the game, his condition had worsened, with the club initially believing he was dealing with a viral infection.

He was placed on antibiotics as a precaution.

However, the night before the match, the Broncos forward began feeling pain in his right side.

"I didn't think anything of it," he said.

The symptoms escalated after the game when Jensen began coughing up blood and experienced breathing difficulties with the Broncos' doctors.

Before the CT scan in Brisbane, it was initially suspected he had pneumonia, but doctors made a far more serious discovery.

"During the scan, they said they needed to get me to emergency, my lung was full of clots," Jensen revealed.

The Broncos forward spent nine days in hospital as doctors worked to stabilise the condition.

Doctors are still unsure now, as they were in April, what caused the blood clots to form, with Jensen using his degree in sports science to explain that these cases normally begin in the legs before travelling to the lungs.

Jensen has to wait three months before they make any decisions about contact training and see whether his lung capacity has improved.

"I can't do anything while I'm on blood thinners, contact-wise, they want to make sure all the blood clots are gone, and I can just do the field-based stuff and get my lungs back to the capacity they were before hand and get my strength back up," he explained.

The uncertainty has been one of the most difficult aspects of the recovery process.

"The hardest part is the unknown," he admitted.

Jensen said even with his medical understanding, the cause of the condition remains difficult to explain, ruling out any family history of blood clots, noting the blood clot he had in his leg last season.

"They say in a lot of these cases, they don't understand why you get blood clots. Some people's bodies are more prone to clots than others. That could be my case."

Despite the seriousness of the diagnosis, when asked whether he has thought about retirement, he responded: "It hasn't crossed my mind."

Instead, his focus remains firmly on returning to the field.

"I am still training as much as I can on the field and keeping my strength and fitness up in preparation to get back.

"I plan to be back and play the last few rounds with the boys and hopefully get the all clear to play."