Is a sudden change in tolerance for alcohol concerning. a single small glass of wine is making me slur and unsteady. no med change.

Check with doctor: This is unusual but you would need to check with your doctor and definitely avoid any alcohol. Alcohol is cleared by the liver and your doctor needs to know what is happening and order some blood tests to make sure that your liver and kidneys are working properly. I would also avoid tylenol (acetaminophen) and medications like motrin or aleve until you check with your doctor.

Altitude change?: A sudden lower tolerance to alcohol can be caused by several things include changes in altitude, level or tiredness, or how much has eaten beforehand. Also, have you donated blood or plasma recently? --that can definitely do that.

Possibly: a decrease in the ability to digest alcohol, a change in the gut metabolism of it (grapefruit juice gums up the gut metabolism) will increase the amount of alcohol. BUT this is more the effect than the accumulation, and other sedatives (generally medications) will interact with alcohol. Without an actual examination, I cannot give specific medical advice on your particular health