I bet he might think it's fake.

yeah I was once accused of faking a miscarriage... which happened while I was at work the week before.

They can think it's fake all they want but if you can prove it you're in the clear.

I had plantar fasciitis and had to still work 8-9 hour shifts on my feet and be lifting things in the stock room, mopping, etc. It was either do that or get fired. I finally couldn't take it any more after about a month of that and quit and found another job that I enjoy much more and where they are more understanding. Not saying that quitting is the answer for OP (I don't know what their circumstances are), but there are other options if OP's boss is being unreasonable with this.

I have that, it's excruciating.

Wait, so OP's boss is both an asshole and a dick? Well then, he can go fuck himself, can't he...

you have clearly never worked a corporate job. All bosses are as described.

My thoughts exactly. Wouldn't op's state get worse by not letting their body rest a little by taking time off?

exactly his boss may have a lot of people to manage and cant hold up production on one sick guy. Notice he said replace not fire. That often just means pulled from the line for the day.

You can be fired at any time for any reason or even no reason at all unless you have a contract that states otherwise. Most work places are "at will" employers.

Is there not laws to protect you against that? I've been chronically ill for years, the last 3 years I have missed 100-150 days of work each year and they can't fire me because my doctor backs me up. (I'm pushing to be on longterm disability because this isn't good for me or my employer).

Not when you are an "at will" employee or as in that particular case I was an independent contractor (construction company. basically reclassifying you as a scam to avoid paying overtime, workmans comp etc.) So technically I was not fired but my "services" were no longer required as he put it.