For normal operations the helicopter would fly at between 1000 feet - 1500 feet above ground level, but ideally we fly clear of cloud, so it could be lower.
The aircraft type is cleared for flight much higher than that, although the highest we realistically fly is about 5000’, we would require oxygen to go above 10,000’ and we would need oxygen for the crew, which we don’t carry. The lowest height is 500 feet, unless we are taking off or landing in order to reduce noise or nuisance to people on the ground.