Whether a diver with Hepatitis C (HCV) should dive depends upon several factors:
-Stage of his disease
-Level of hepatic involvement
-Type of treatment he is receiving
-Original cause of his HCV (drug injections?, etc). 28% of all HCV infections are from injectable drug use.

A diver with this disease needs to be in relatively good physical condition (from a conditioning standpoint), have no severe liver involvement with cirrhosis and under no dangerous treatment protocol that would injure the immune system. Newer therapies for HCV include drugs that cause severe suppression to the immune system, making it highly dangerous to dive even in relatively clean water.

The poorly conditioned and the cirrhotic should not dive; the person with even the slightest possibility of drug use should not dive.

Medications include Interferon and Ribavarin

Side effects of interferon alfa (* Indicates adverse to diving)
Early
Flu-like illness*, chills, fever, malaise*, muscle aches, headache*, poor appetite

Later – common
Weight loss
Increased need for sleep *
Psychological side effects (irritability, anxiety, depression)**
Hair loss
Thrombocytopenia (low platelet count can cause bleeding)**, leucopenia (low white count increases susceptibility to infection)**

Unusual or severe
Seizures ***
Acute psychosis **
Bacterial infections **
Autoimmune reactions *
Hyperthyroidism or hypothyroidism or transient thyroiditis *

Rare
Proteinuria
Myocardiopathy *
Rashes *
Interstitial lung disease *
Retinal changes
Ototoxicity*

Ribavirin has the following side effects:
Anemia**
Insomnia
Fatigue
Anorexia
Headache
Nausea

Marine infections, particularly Vibrio vulnificus are more likely to happen in the immunosuppressed.