There are two types of Diabetes Mellitus; Type 1 and Type 2.

Type 1 is where the victim's pancreas cells get attacked by the body, because the body thinks it's a virus. The pancreas is where insulin is produced. Insulin is the liquid in the body that breaks down sugars; if insulin isn't in the body, sugar levels can rise. This is known as "hyperglycemia".
Type 1 and 2 can be found in animals, and without proper treatment, these animals can die quickly.

Diabetes isn't a birth mutation. You rather get it when you are older.
Type 1 is known as "juvenile diabetes"; Type 2 is known as "adult onset diabetes"

Juveniles are more known to get type 1(however adults can get it too) while type 2 can be obtained at any age due to not enough insulin being produced.

I was thinking if diabetes mellitus was put into the game, type 1 would be more centered around adolescent lions.
The warning would come before the cub turns 1 year old. I'm not sure if there is a herb that is like insulin, so no cure could be obtained.

SYMPTOMS OF TYPE 1(in game)
- The cub would get noticeably skinnier and skinnier each day that goes on.
- The cub's hunger wouldn't go up as much when fed.

SYMPTOMS OF TYPE 1(in real life)
- Excessive hunger and thirst
- Blurry vision
- Frequent bedwetting
- Weight loss
- Sleepiness
- Nausea/vomiting


Notes
Please understand I am a type 1 diabetic. I know about the disease, however I could be wrong at some points. If you know about it and I missed something, please don't hesitate to tell me
Anything you would like me to add, ask.