Lil Keed complained of severe stomach pains in the days leading up to his untimely death on Friday.
The 24-year-old rapper told friends his stomach pain was so bad, he had to go to a hospital.
Sources say Keed was addicted to lean, also known as purple drank and sizzurp. The main ingredient in lean is prescription codeine cough syrup.
The concoction of cough syrup and hard candy in a soft drink is favored by rappers like Lil Wayne (pictured).
Multiple sources tell TMZ, the YSL rapper battled with drugs and alcohol over the years, but he was clean and went to an L.A. hospital to be evaluated after suffering from stomach pain.
His condition got progressively worse, and his organs - liver and kidneys - began to fail, causing his painful death.
Keed (right) was signed to Young Thug's YSL record label in Atlanta.
Before he died, Keed denied YSL was a gang. But a Fulton County prosecutor said YSL was a front for violent street gang activities.
Young Thug (left), rapper Gunna (right) and 26 other YSL members are currently sitting in the Fulton County Jail without bond in Atlanta. They are charged with violating the state's RICO laws and criminal gang activity.
Keed was not named in the 56-count indictment.
Mixing codeine or heroin with synthetic opioids like fentanyl further increases risk of death.
Worldwide, about 500,000 deaths are attributed to opioid overdoses.