Unfortunately, yes the VA can take away your disability rating.
Generally, the VA takes away ratings because:
1. The veteran’s service-connected condition has improved.
2. The veteran was receiving TDIU benefits and went back to work.
3. The veteran’s cancer has gone away and treatment is no longer needed.
4. The VA made a mistake. Veterans can appeal if a rating is taken away.
5. The VA ordered a reexamination and found the veteran’s ratings incorrect.
Learn more about why the VA reduces ratings here: