When rewiring a house, does a microwave have to to be on it's own circuit?

No. A microwave oven does not draw so much current that it needs its own circuit. However, it's not a bad idea to use one of those outlets with built in breakers where you plan to plug in your microwave to prevent needing to go to the circuit box if you happen to overload the circuit.

When rewiring a house, does a microwave have to to be on it's own circuit?
If it is built in or fixed in place such as an over-the-range unit YES, it does need it's own circuit.
Counter top units do not, but it is a good idea.

However, it's not a bad idea to use one of those outlets with built in breakers where you plan to plug in your microwave to prevent needing to go to the circuit box if you happen to overload the circuit.Got a link to such a thing? In over 25 years I have never seen anything like that.

Got a link to such a thing? In over 25 years I have never seen anything like that.
Looking further into it, I was specifically referring to a GFCI outlet. This is not what I thought it was. This is what I get for knowing only enough to be dangerous.

Yeah, I was wondering about that.

A GFI is NOT a "breaker" or overcurrent device. This is a common misconception by DIYers and lay folks.

You must refer to the manufacturer's instructions for any appliance or device and provide what is required.

If it is built in or fixed in place such as an over-the-range unit YES, it does need it's own circuit.
Counter top units do not, but it is a good idea.
stanfortyman,
This relates to the other issue you've been helping me with where I wanted to hardwire my microwave.
If the microwave is considered fixed-in-place and needs its own circuit, does this mean its receptacle cannot be a duplex receptacle because of the potential of plugging something else in?