What Is a Viral Load for Hepatitis C?

Measuring viral activity tells us how effectively a treatment is working

A viral load is simply the measurement of the amount of virus in your blood. Viral load measurements are commonly used to monitor chronic viral diseases such as HIV, hepatitis B (HBV), and hepatitis C (HCV).

Electron micrograph of hepatitis C virion (HCV)
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In the case of HCV, a test called a quantitative HCV RNA assay is used to measure the virus's genetic material (RNA) detected in a milliliter of blood. Other technologies can be also used to monitor viral activity, most of which do so by detecting either viral DNA or RNA.

Why Viral Load Is Important

Healthcare providers use your viral load to determine how well you're responding to anti-viral treatment. Typically your viral load will be tested before you start therapy (for hepatitis C, for instance) and then repeated periodically to measure how you are responding. At least two viral load results are needed to assess treatment efficacy.

A significantly reduced viral load, like a 100-fold decrease in viral actively, generally means that treatment is working. Ideally, a person would achieve a so-called "undetectable" viral load, meaning that the current testing technologies are unable to find any evidence of the virus in blood samples.

It's important to understand that while the test is valuable in predicting treatment outcomes, it does not tell you anything about the severity of your liver disease. Typically, liver biopsies and imaging tests (for example, ultrasound or MRI) are needed for that.

High vs. Low Viral Load

Insofar as viral hepatitis C is concerned, a high viral load is usually over 800,000 IU/L, while a low viral load is under 800,000 IU/L. This range can vary significantly, however, based on what is considered average in a specific region or population.

It's important to note, however, that a viral load of 800,000 IU/L does not mean you have 800,000 actual viruses in your blood. Rather, it means that the lab has determined there are 800,000 international units (IU) in a liter of blood. An IU is a standard measurement used by pathologists to ensure consistency from lab to lab and is considered more accurate than a simple "head count" of viral RNA.

Typically speaking, though, 800,000 IU/L correlates to around two million copies of viral RNA. 

Undetectable Viral Load

The period of remission (undetectable viral load) 12 weeks after completing hepatitis C therapy is known as a sustained virologic response (SVR), or SVR12. Nearly all people who achieve an SVR12 go on to achieve an SVR24, which means there has been no viral activity detected 24 weeks after treatment.

An undetectable viral load does not necessarily mean you have no virus in your blood or that you've achieved a cure. However, if you are able to sustain an undetectable viral load for a period of 12 weeks (and this usually extends to 24 weeks), the likelihood of the virus reappearing (rebounding) is considered extremely low.

While tests can vary in terms of sensitivity, which means their ability to detect the virus, most current assays are extremely accurate.

A Word From Verywell

While the tests involved in diagnosing and treating hepatitis C may seem complex, try not to get too bogged down in the details. If you do have hepatitis C, remain active in your liver health by seeing a healthcare provider who has experience treating people with hepatitis C.

Take your medications as instructed and remain in close contact with your healthcare provider. With proper care, the good news is that you can clear the virus from your body (and essentially be "cured").

Hepatitis C Doctor Discussion Guide

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2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. U.S. Department of Veterans Affairs. Hepatitis C viral load / HCV RNA quantitative testing.

  2. Burgess SV, Hussaini T, Yoshida EM. Concordance of sustained virologic response at weeks 4, 12 and 24 post-treatment of hepatitis c in the era of new oral direct-acting antivirals: A concise review. Ann Hepatol. 2016;15(2):154-9. doi:10.5604/16652681.1193693

Additional Reading
  • Gupta E., Bajpai M, Choudhary A. Hepatitis C virus: Screening, diagnosis, and interpretation of laboratory assays. Asian J Transfus Sci. 2014 Jan-Jun;8(1):19-25.

  • University of Washington. Hepatitis C Online: Goals for treatment and predicting response

By Charles Daniel
 Charles Daniel, MPH, CHES is an infectious disease epidemiologist, specializing in hepatitis.