I’m not sure how to answer. Live at sea level, and when going up to Truckee / Lake Tahoe (elevation 5800-6200 feet) its not easy to detect shortness of breath, but if quickly climbing stairs I’ll feel it. Same with Reno at elevation 4500.
Slight headache, slight nausea, dehydration - really only feel those things above 9000’ for example going up to Breckenridge Colorado (elevation 9600) for a couple days. One of my worst ‘hangovers’ was going from living in Portland (sea level) to Breckenridge with friends to ski, and having a couple beers the night we arrived.