Hi my grandfather is 90 years old. he had a cold for a week and now when he's at home, every time he gets up he's very weak and has trouble walking. w?

May be dehydrated: It's possible he may be dehydrated and that can cause the symptoms you describe. Ideally an evaluation by a doctor is what you should have done. You probably should have him evaluated in the er.

May be a problem: An infection of any kind, especially with a fever can make chronic neurological problems seem worse. If he has parkinson's disease, a prior stroke, or peripheral neuropathy, or prior low grade muscle problem, he might show more symptoms. However, an area of focus might be recent meds, either prescription or otc, as these could cause adverse reactions.