According to a news report, Kim Jong-un underwent surgery at a hospital located in Hyangsan on April 12. This news source from South Korea originated from the Daily NK, a news source controlled by North Korean writers that defected from North Korea. It further stated that Kim Jong-un experienced difficulties with his health due to smoking, obesity, and exhaustion. Since the surgery, he was transported to a private treatment facility. This explains his prolonged disappearance from the government.  Additionally, news sources reported that his last public appearance was on April 11. After leading a meeting, Kim Jon-un was transferred and admitted to the hospital. This is not the first time Kim Jong-un disappeared from the public eye because of medical issues. In 2014, he disappeared for almost six weeks before coming back with a walking stick. South Korea claimed that he left for surgery on his ankle. North Korean news confirmed that Kim Jong-un suffered from a medical issue. Therefore, it is likely that Kim Jong-Un is in the hospital since he has disappeared for medical issues before. 
South Korea's chief policymaker denounced the rumors surrounding Kim Jong-un's health in a statement. He claimed that the South Korean government investigated and found "nothing unusual."  Donald Trump also claimed that the rumors were false, finding no basis for believing Kim Jong-un's heath was in danger. 
[P1] A South Korean news report claims that Kim Jong-un is in the hospital. [P2] Kim Jong-un has disappeared for medical reasons in the past. [P3] Therefore, Kim Jong-un is in the hospital.