All the patients suspected of viral hepatitis are tested for hepatitis viruses A, B and C: IgM anti-HAV, HBsAg, IgM anti-HBc, anti-HCV. If any of these markers are positive, there are conducted further serological tests to differentiate acute infection from chronic infection or past infection. If there is confirmed the presence of hepatitis B virus, anti-HDV (antibody to hepatitis D virus) is measured.
Tests for IgM anti-HEV (IgM antibody to hepatitis E virus) are measured if the patient is (or have recently traveled to) an endemic area and if the test is available.
In uncertain cases HCV-RNA and HBV-DNA can be measured, although these are sophisticated tests and are not routinely available.

At its onset, acute hepatitis mimics various non-specific diseases. Usually, hepatitis is suspected only when jaundice develops. At this stage hepatitis should be differentiated from other disorders associated with jaundice.
Hepatitis diagnosis includes non-specific liver function tests: aminotransferases (ALT and AST), bilirubin, alkaline phosfatase, etc. AST and ALT are usually highly elevated in hepatitis (> 400 IU/L) and ALT is usually higher than AST. The level of aminotransferases not always correlates with clinical severity of hepatitis, which means that ALT and AST can be markedly increased, but the evolution of hepatitis can be relatively mild, and vice versa.
Hyperbilirubinemia can be variable in hepatitis and usually is preceded by urinary bilirubin (darkening of urine). Alkaline phosphatase is moderately elevated in hepatitis.
If viral hepatitis is suspected, it is necessary to effectuate serological studies, to determine the type of virus.

Jaundice, also called icterus, represents a condition characterized by the yellowing of skin, sclera (white of eye) and other tissues, caused by excessive blood bilirubin levels.
The normal level of bilirubin is about 0.5mg/dL. Jaundice becomes visible only when the level of bilirubin exceeds 1.5 mg/dL.
Jaundice causes arte classified into three categories: pre-hepatic causes, hepatic causes and post-hepatic causes.
Jaundice is a frequent sign in hepatitis. Hepatitis, as a cause of jaundice is classified into hepatic causes category. In hepatitis jaundice is usually preceded by the darkening of the urine and discoloration of stool. Also, jaundice is frequently associated with skin itchiness (pruritus), especially in post-hepatic jaundice (also called obstructive jaundice).

Acute hepatitis evolution has several phases. First is the incubation period, when the virus multiplies and spreads. This period is asymptomatic (shows no signs). The second phase is the prodromal period, which manifests with such symptoms as anorexia, nausea, vomiting, fever and, possibly, dull pain in the right part of the upper abdomen. Than follows the icteric period, characterized by jaundice and preceded by urine darkening and, sometimes, itchiness. During this phase the liver is usually enlarged and sensitive to touch. Jaundice period can last up to 2-4 weeks.
Hepatitis evolution can be mild, with no jaundice and sometimes can show no symptoms at all. These patients present a high risk of infection for the others, as long as they do not know that they have hepatitis.