Mitochondria are small organs in your cells. They help convert the food you eat into the energy you need to function.

If the mitochondria aren't working properly, cells must make energy in a different way. When this happens, a chemical called lactic acid is produced.

Lactic acid changes to another form called lactate in the blood. Lactate is then broken down by the liver. If your cells produce too much lactic acid, your liver may have a hard time breaking down the lactate fast enough.

Higher than normal levels of lactate can build up – this is called hyperlactatemia. When levels get very high, lactic acidosis can occur. The body can often cope with hyperlactatemia, but lactic acidosis is a serious illness that can be life-threatening.

Lactic acidosis can develop when your cells make too much lactic acid or when your liver isn't working properly. HIV drugs in the nucleoside reverse transcriptase inhibitor (NRTI) class can sometimes cause these problems:

• Cells make too much lactic acid: NRTIs can damage the mitochondria. This is known as mitochondrial toxicity. It can cause the mitochondria to have trouble making energy. Lactic acid is made by cells that aren't getting enough energy from their mitochondria.
• Liver isn't working properly: NRTIs can cause the liver to become fatty, a condition called hepatic steatosis. A fatty liver doesn't work well and can't break down lactate efficiently.

It is a rare side effect of the NRTIs, especially Zerit (stavudine, d4T), and Videx (diadanosine, ddI).

The symptoms of lactic acidosis include:

• Persistent nausea, vomiting, and abdominal pain
• Unexplained tiredness
• Shortness of breath
• Rapid breathing
• Enlarged or tender liver
• Cold or blue hands and feet
• Abnormal heart beat
• Weight loss

It’s important to get in touch with your health care provider right away if you experience symptoms. Early identification of lactic acidosis is very important. The condition can cause death if it’s not caught early and treated.

Your health care provider should perform a physical exam to check for an enlarged liver and may order a CT scan or ultrasound of your liver. You will probably also have some blood tests done including:

• Liver function tests
• Electrolyte level
• Blood pH level
• Lactate level

Treatment will depend on your symptoms and lab test results:

• A normal lactate value is less than 2 mmol/dL. If your lactate value is more than 2 but less than 5, and you have none of the symptoms of lactic acidosis, your health care provider would probably continue your HIV drugs.
• If your value is more than 5, and you have symptoms of lactic acidosis, your health care provider would probably stop your HIV drugs as this is getting into the danger zone.
• If your value is more than 10, and you have symptoms, you have outright lactic acidosis. Your health care provider would stop your HIV drugs and you would be admitted to the hospital for treatment. Lactic acidosis at this stage is a medical emergency.

There is no proven treatment for lactic acidosis other than stopping the NRTIs. In serious cases, hospitalization and supportive care, such as intravenous (IV) fluids and a machine to help you breathe, may also be needed.

Some health care providers recommend giving thiamine (vitamin B1), riboflavin (vitamin B2), L-carnitine, coenzyme Q, or vitamins C, E, and K to people with lactic acidosis, but the these treatments have not been proven to be effective.

You should not stop taking any HIV drugs without talking with your health care provider. If you are diagnosed with lactic acidosis, your health care provider can help to decide how to stop your HIV drugs, when to restart, and which ones to take when you go back to treatment. If you have only slightly elevated lactate levels and no symptoms, you may not need to change your HIV treatment regimen.

Certain factors put people at higher risk for lactic acidosis, including:

• Treatment with Videx and/or Zerit (when used together, the risk is even higher)
• Treatment with ribavirin (for hepatitis C)
• Treatment with Glucophage (metformin) (used to control diabetes)
• Obesity
• Female gender
• Poor liver function

Because there is a connection between liver problems and lactic acidosis, make sure that your health care provider checks your liver function while you are taking NRTIs, especially if you have a history of heavy alcohol use or a liver problem.

Many people on HIV treatment have elevated lactate levels. It usually doesn’t cause any problems. For that reason, it is not recommended that lactate tests be done on a regular basis. However, if you experience any of the symptoms of lactic acidosis described above, tell your health care provider.

Although lactic acidosis is life-threatening, it is very rare. The point of learning about lactic acidosis is not to scare you. It’s to help you be aware of what’s going on in your body. That way, if you recognize any symptoms of lactic acidosis, you can tell your health care provider right away and get checked out.