How often do a person need to drink before you could consider a person an alcoholic?

Alcoholism. Alcoholism is when you have signs of physical addiction to alcohol and continues to drink, despite problems with physical health, mental health, and social, family, or job responsibilities. The amount of alcohol that can increase the risk of developing alcoholism include 15 or more drinks/week for men, 12 or more drinks/week for women, and 5 or more drinks/occasion at least 1x/week for any gender.
No magic amount. It is not a question of how much a person drinks, but rather what happens when they drink. Some people get into trouble with 4-5 drinks, get into fights, arguments, drive cars, make bad decisions, with relatively little alcohol, while others may drink more than that on a regular basis without issues. If you drink you intended, it causes trouble for you, but you can't stop/cut down, it's a problem.