When my parents lay in bed, I'm going to raid their medicine cabinet.
Why are you looking through your parent's medicine cabinets?
Anything I can find!
Your parents are prescribed medicine for their own medical needs and it's wrong for you to take their medicine. Not only will you bring physical harm to yourself by using their medicine, you will also cause them to be low on the doses that they may need to be healthy.
They can get more at the pharmacy when they run out.
Maybe they can, but something as simple as blood pressure medication could cause your death. This is why you should NEVER take someone else's medication.