Garbrandt (11-3) told ESPN on Thursday he has been hospitalized in New Jersey since last weekend, and is currently on his way to Cleveland to see a specialist. A time frame for his return is currently unknown, although the 28-year-old said he hopes to be back as soon as possible.
"I honestly don't know what it is," Garbrandt told ESPN. "A month ago, I had cellulitis in my shin. I went to the hospital and got that cleared with antibiotics. I got back into training, but then last Friday, the lymph nodes in my groin were inflamed and I didn't feel well. I thought it was just due to rough training.
"On Saturday, I had flu-like symptoms. The lymph nodes were so inflamed I couldn't walk. I took an Uber to the hospital and did a bunch of tests on my blood, kidneys, CAT scan. The doctor sent me home and 20 minutes later I felt even worse and started pissing blood."
Garbrandt said he tried to sleep it off on Saturday, before readmitting himself to the hospital on Sunday. He has been under supervision all week and is feeling better, although doctors still haven't been able to diagnose the issue.
Originally from Uhrichsville, Ohio, Garbrandt said he's hopeful the UFC will rebook his fight against Assuncao at a later date, but added he'd understand if Assuncao took another opponent.
Garbrandt cross-trains with Team Alpha Male in Sacramento, California, and striking coach Mark Henry in New Jersey. The former champion is looking to rebound from an 0-3 skid, during which he lost his title to rival and former teammate TJ Dillashaw.
"This was such an important fight for me, not only fighting in my home state but getting my comeback started," Garbrandt said. "I need to focus on my health right now, but I'm not ruling out a quick turnaround. I'll be trying to get back as fast as I can."