Hepatitis C is much more common among people who use drugs and alcohol than the general population. Some doctors may refuse, or be reluctant to treat, people who are using illicit drugs and alcohol—even when they need treatment and are ready and willing to undergo therapy.

Illicit Drug Use

Several studies have reported that illicit drug users can be safely and effectively treated for hepatitis C; in fact, cure rates are similar to those of non-users. Comprehensive care and treatment seems to be the most effective for people who are using drugs, providing them with access to both medical and mental health care, peer support, harm reduction services and addiction treatment.

HCV treatment decisions for people who are using illicit drugs should be made on an individual basis. All illicit drugs are not the same, and neither are all illicit drug users. Some can easily manage HCV treatment, while others may choose to wait until they feel more stable (see the next section, "What if I'm using methadone or buprenorphine?").

Showing up for medical appointments may be a better gauge for who is likely to getting through HCV treatment than whether or not someone is using illicit drugs.

Some doctors are concerned that injection drug users may be reinfected with hepatitis C after being cured. Although this has happened, it is not common, and medical providers can help injection drug users to prevent reinfection by referring people to needle exchange programs and/or prescribing syringes.

Alcohol Use

Alcohol blunts the immune responses to hepatitis C, which may be why heavy drinkers generally have higher hepatitis C viral loads than non-drinkers. Regular alcohol intake (especially more than 4 drinks per day for men, and more than 2 per day for women) is known to increase the rate and severity of liver damage in people with hepatitis C; it also increases the risk for liver cancer.

Studies have linked both lifetime and recent alcohol use to poorer HCV treatment outcomes, but these used less effective treatment than the current standard of care, and adherence was not measured. A more recent study suggests that poor treatment adherence, not actual alcohol intake, may be lowering cure rates. In the meantime, many doctors will not treat drinkers until they are willing to enter treatment, or until they have been abstinent for six months.

On the other hand, some doctors have reported that starting HCV treatment leads to other healthy behaviors, such as cutting down or eliminating alcohol intake. It’s important to find a doctor that you are comfortable working with, and to decide if—and when—you want help to cut down or stop drinking

A Word About Marijuana Use

Researchers have found that marijuana use can be harmful for people with hepatitis C. Daily marijuana use increases fat buildup in liver cells (a condition called steatosis), which can worsen liver scarring. Researchers have also found that daily users are more likely to have serious liver damage than occasional users or non-users.

In contrast, one study reported that modest cannabis users were more likely to complete HCV treatment and to be cured by it than non-users, because marijuana helped them to manage treatment side effects.