Is it necessary to have a head ct after i bumped my head on a microwave door one week ago? everything normal except for some headaches.

Probably OK: If your headaches get worse, continue unabated or you develop any other abnormalities go and see a doctor. You would have had to hit yourself very hard to result in a subdural hematoma, but always better to be safe than sorry.

Not necessarily: You may have sustained a mild concussion when you bumped your head. Headaches can be a symptom of post-concussion syndrome which can last for a few weeks after the injury. Ct scans are usually needed if you are having vomiting, changes in behavior/confusion, or persistent severe headaches.