How to treat anxiety symptoms (tinnitus, constant lightheaded) that caused by to many drinking caffeine? how to check if i'm overdose? blood test?

Easiest way: The easiest way to determine whether caffeine is causing or exacerbating anxiety is to stop using it for a time -- and see if symptoms go down. Be aware that if you're accustomed to drinking many cups of coffee, caffeinated soda, energy drinks, etc daily, you may have some withdrawal symptoms for a couple of days. Headaches, flu-like symptoms, tiredness, etc. Tapering could be better.

If you have symptoms: It is overdose, no need for a blood test. Gradually reduce your intake of coffee since you know that this is the cause of your symptoms. See this site for more information. http://www.nlm.nih.gov/medlineplus/ency/article/002579.htm.

Taper off caffeine: There's no blood test (that i'm aware of) for caffeine, and the best thing to do for chronic overdose is to gradually decrease your use over a number of days or weeks. (if you stop all at once, you may get bad headaches or other withdrawal symptoms.) decreasing the caffeine is the only "treatment" that makes sense. If your symptoms persist without caffeine, see a doctor. Good luck!