How can you tell if someone has a drink problem?

They might:

develop a tolerance so need to drink more and more for it to have an effect.
be unable to cut down the amount they drink.
drink at inappropriate times
smell of alcohol during the day
have a craving for alcohol
become trapped in a cycle of drinking and recovery.
be unable to meet their daily responsibilities
continue to drink despite dangerous situations (i.e. driving)
withdraw from normal life and avoid contact with family and friends
appear tired, unwell or irritable for no reason
experience alcohol withdrawal symptoms when not drinking (nausea, sweating and shaking)