You pick up the lead, and your dog starts whining before the door is open. If they are loose-bodied and bouncing toward it, excitement may be driving the noise. If they duck from the harness, freeze, pant, or retreat, the same sound may come with worry. Watch the dog, not only the volume.
Check that their harness fits and does not rub. If the whining is new, comes with sensitivity to touch, or continues once outside, speak with your veterinarian. Do not force a harness onto a dog who is showing fear or aggression. Use another safe toileting plan while you rebuild comfort.
Lower the rush
On an easy day, pick up the lead, place it down, and reward a moment of relaxed behavior. Practice walking toward the door and returning without leaving. Keep each step short enough that your dog stays comfortable. If they are excited, wait for a few paws-on-the-floor moments before opening the door, then reward calm movement into the hall. Do not insist on a long silent sit before every outing, especially when your dog needs the toilet.
For a worried dog, introduce the harness separately from the walk: let them investigate it and reward voluntary steps toward putting it on. Gradually add fastening and movement only while they remain relaxed. If opening the door or the outside route is the hard part, change that piece instead of repeating the lead exercise.
A quieter departure starts with learning what your dog expects when the gear appears. For the skills beyond the doorway, see the everyday leash-walking guide, first work out whether your dog is excited or worried about leaving
Sources: Dogs Trust: How to train your dog to wear a harness. Dogs Trust: Why dogs get scared or frustrated and how to help.