Originally Posted by
biminiblue 
Well, as an alcoholic myself I can tell you that this isn't necessarily true - though it may be. No way to know.
There is a phenomenon called Reverse Tolerance in long-term alcoholics and it is when there has already been damage done to the liver/organs. You can Google that.
Toward the end of my drinking, one day my tolerance would be "normal" (ie I could drink a 12 pack easily and function relatively well) and the next I would black out after 3 drinks. When I checked in to rehab my bloodwork was in the high-normal range. An alternative theory is the possibility of mixing benzo's (valium / Xanax, etc.) with alcohol - which is dangerous but not uncommon.
However, it really doesn't matter how or why this is occurring. The question is what are you going to do in terms of your boundaries?