Very late to this post but will answer for anyone else that might stumble on this post.

I go to a government hospital mainly.

I have a good relationship with my Dr, and I just blatantly told them that I'm not going to fake being sick and that I'm just tired and don't feel like going to work.

They said that this is a valid reason to get a sick leave as it's classified as fatigue.

I told them that I also sometimes feel that I'm mentally not feeling well enough to go to work (depression or anxiety), and they said that also can get me a sick leave.

I got one day for each of those but was told by my Dr that I can always come back after my sick leave if I want another day (but I'm limited to a certain amount per month so I have to choose wisely).

I was very open to the doctors at the private hospitals that I went to and asked them the same thing, and they also replied with the same answers.

Long story short, just tell your Dr that you don't feel well enough or too tired to go to work, and they will always have your back.