Prescribe Benadryl 200mg 3 times per day for long term effects of Stevens Johnson Syndrome. Been taking this dose for 7 months. By complete accident I took 600mg.
Not recreational use.
I took morning dose fine. I took lunch dose and did not get my normal relief. I then thought I had not taken my lunch dose, so I took the lunch dose again.
After that dose I had an in-office procedure for which I had an IV. I left the office and went home and took my normal meds. By this time I had started shaking, feeling unwell & I feel 'drugged' and not myself. The Doctor's office called- I had been given a dose of Benadryl to alleviate any issues with the radiology contrast.

I do not feel well but...
No heart palpitations
No difficulty breathing.
Somewhat confused - not delirious.
I'm very shaky.

Would this dose (with my tolerance level) sort itself out or should I head to the ER?

You need to call Poison Control 800-222-1222. They will tell you what to do.

AntC, we can't assume that he resides in a particular country.

The poison control office will be in your phone book or online. It would be good to call. That is beyond the recommened natural dose and is a cause for concern, but I don't think it is life threatening. Talking to the poison control will let you know what steps you need to take, which might be to go to the ER if you haven't already, than you can follow up with your doctor. It might be also wise to invest in a daily/weekly pill box. You count out and separate the pills for each day, and at each time, before hand. This often prevents mix ups like this. Also need to know what they're giving you when you go in for your treatments.

You are correct, Craven. I had assumed the OP was in the US because they used the name brand Benadryl and not the generic name

That's completely fair.

I use benedryl in Canada, I have bought it in England and china too.