When you can't function without it.
when u tell urself ur not gonna drink....and u do....and u lose control over the amount....and what u do...then u tell urself u'll control it...just have a few.....and u really mean it....and then b4 u know it u've lost control over the amount...and ur behavior....and u repeat this merry-go-round over and over....when it begins to affect u legally,financially,ur marriage, ur kids,lose friends,just associate w/drinkers,drink alone,drive drunk,have blackouts......i think u get the picture!
when it goes from something you want to do occasionally, to something you need to do to function. One of the first signs of alcoholism is getting the shakes when ur not drinking