Hey April, You can definitely still use extensions even if you have thin hair, I've seen them done on people recovering from chemo with hardly any hair at all. However, I would be careful not to use them too much since they can pull on your hair and cause it to break (aka, make it even thinner). Have you tried Biotin or Viviscal supplements? They can help your hair grow more and make it thicker. It takes a few months to start to see results, but I've had a good experience with Viviscal (and you can get it at the drugstore or on amazon). Hope this helps!