Why is my cat losing her hair on her back from the base of her tail forward to the mid of her back?

my cat also having the same problem.

from my observation, this may due to her old age (for my cat's case)

there may be other reasons as well.

for example allergic to certain kind of food, and etc.

if your cat is severely losing her hair on her front legs or any part of the body, do take her to the vet.

but if the condition is not severe, then it is a normal condition and the hair will grow back later on.