Yes, if you have an illness that takes you well beyond available paid sick days (usually around 5 to 10 days a year depending on employer), it is common that you will be fired and lose your job entirely. Some workplaces are more compassionate than others but not many
When this happens you lose your insurance too, usually at the end of the month. You can pay around $800-1200 a month to keep it though, more if there’s a spouse or kids