2001 yukon low coolant

I have a 01 Yukon that displays low coolant. I add coolant (about 1/2 gal) and everything is fine for about a month or so. Same thing happens again. I don't notice any fluids on the ground and nothing from the exhaust. What should I be concerned about? I have the bigger v8.

Thanks
Dan

Is the passenger side floor board wet, or a filming of the inside of the windshield when the defrost is used, (heater core) ?

How's the oil on the dipstick look, color wise ?

Has the vehicle been running hotter than usual ?

Sorry about all the questions, just trying to get some background.

No wetness on the floor. No condensation or filming when defrosting. Oil looks ok. Temp is where it always is. Seems to come up to temp normally. Heat works fine.

Thank you for your help.

Is your Yukon an XL ?

No a Yukon SLT.

Can you park the vehicle in a dry area after prolonged running to see if there is any noticable leakage on the ground ?
Can you see under the water pump area to see if there might be signs of leakage ?
If possible take a look at your freeze plugs and see if any of them might be leaking.
Given the amount of coolant you are loosing these will be very small leaks.

Yes I will try that.