Hepatitis C and Viral Load

Medically Reviewed by Arefa Cassoobhoy, MD, MPH on September 19, 2023
3 min read

Your viral load is how much hepatitis C virus (HCV) is in your blood. Your starting level can give a clue to your chances of success with treatment. Changes in your viral load also can tell your doctor if you’re sticking to your therapy and if you’re getting enough drugs to control your disease.

But your viral load measures only what’s happening in your blood, not your actual liver cells. So it can’t show very well how serious your hep C is, how quickly it might worsen, or how well your treatment is working. It also says nothing about the amount of damage or scarring in your liver.

They check your blood for HCV’s genetic footprints. If any are found, it means that you have active hep C and that your viruses are multiplying. Viral load tests come in two types:

Qualitative: This can confirm if you have hep C or not. A positive test means it found HCV genetic code in your blood. Negative means it found no measurable virus. Qualitative tests are very sensitive, meaning that if you have a current hep C infection, they almost always will find it.

Quantitative: This is often called a hep C RNA test. It measures how much HCV is in about a drop of blood. Most labs now report the numbers as international units per milliliter (IU/mL).

The goal of hep C therapy is to drop your virus count low enough so it’s undetectable. If that’s the case 3 months after you finish your treatment, you’re considered cured. This happens in more than 90% of people who get the recommended treatments.

High viral load: This is when your count is more than 800,000 IU/mL. If your viral count is high at the start, it can be hard or impossible for your treatment to completely get rid of the virus. Some researchers consider high levels anything above 400,000 IU/mL.

Low viral load: This is a count below 800,000 IU/mL. Your odds that treatment will make all or most of your HCV go away are better than with a high viral load.

Undetectable viral load: This doesn’t necessarily mean you have no viruses. Undetectable levels can differ, depending on how precise your test is, the lab you use, and how it handled the blood sample. You still may have viruses, but too few for the tests to pick up.

Two newer tests -- transcription-mediated amplification (TMA) and polymerase chain reaction (PCR) -- can measure as few as 5-10 IU/mL. A third one, called branched-chain DNA (bDNA), may miss viral loads below 615 IU/mL.

Sustained virological response: This is when the most sensitive tests find no trace of HCV in your blood 12 weeks after you stop treatment. It’s also called a viral cure. It means your disease is in remission and your hep C is no longer active. Your liver may start to heal, and your chances for liver failure and liver cancer may drop. To confirm, you may need to repeat the test or take a qualitative test that checks if you’re negative for any trace of viral genetic material.

Checking your virus count before, during, and after treatment tells your doctor if and how well your drugs are working. A rising viral load doesn’t always mean you’re getting sicker, and a drop in the virus count isn’t a sign that you’re on your way to being cured.

Unlike with HIV, where lower viral counts usually mean longer, healthier life, HCV viral loads don’t say much about how fast your hep C is progressing or how your disease might turn out. For that, your doctor will need to check your liver enzymes and your liver tissues and run other tests.

Usually, your hep C treatment will be the same no matter how high or low your viral load is. Your doctor will use your virus levels to monitor how you respond to the medication. The drugs you’re prescribed will depend less on your viral count than on your overall health, genetic makeup of your HCV, and other things.