migraine or TIA

I'm a 51yo female who cycles on the rd 4-5x/wk.  Yesterday I rode 28 hard miles after taking 2 capsules of SPORTLEGS.  This is a nutritional supplement to support your body's lactate energy system.  This is not a stimulant.  One capsule per 50lbs. I took 2 at 130lbs which is less than rec.  I felt fine during the ride but 30 minutes afterwards I got dizzy and then lost my peripheral vision.  After that I had difficulty saying some words and remembering full names of acquaintances.  This loss of memory subsided over a period of 30-40 min. Today I feel ok with slight headache.  I do not have hx of headaches.  6 years ago I experienced similiar symtoms (symptoms) after taking Phen-free before an intense spinning class 1st thing in the am without eatting.  I had an MRI and full neurological exam all of which came back negative.  The Dr thought it might have been a precursor to a migraine.

[pat05]

im curious what is tIa?