How can you tell if a headache is serious or not?

Not likely serious. Headaches are very common. Most are tension, but some are migraines or cluster. New onset headache in an adult which is recurrent should raise concern and prompt a work up. A cat scan of the brain is a quick test that is inexpensive but lacks details and may not show early stages of a brain tumor. An MRI with contrast is the best diagnostic study.
Associated symptoms. Any headache which has any of the following could be serious: - sudden onset acute pain without any frank initiator - dizziness, numbness, changes in vision, vertigo or vomitting - swelling, masses - fainting - any other abnormal symptoms or feelings.

Related Questions

How can you tell if a headache is something serious? I get headaches in different places and strengths everyday for the last few months.

Get medical exam. The best way for your to get reassurance is to go to your DR, have an exam It is impossible to make a DX for your HA's in this format. Read more...