You find you have to take more drugs to gain the same effect.
You have tried to reduce or quit drugs but find you cannot. Short periods of being clean or in control lead to relapses that become progressively worse.
Your mental /physical health is suffering as a result from your addiction.
You no longer, or rarely, use drugs socially, preferring instead to use alone, away from others.
You choose to buy drugs over basic necessities such as food or paying bills.
You need the drug to function on a daily basis