Before you start taking anti-HIV drugs, or if you need to switch to a new combination, you should have a number of blood tests.

To help make sure that you start with an effective combination of anti-HIV drugs, you should have a test to see if your HIV has resistance to any antiretroviral drugs. This is because it is possible for a strain of HIV that has already developed resistance to some drugs to be passed on to someone who has not taken those drugs.

Your clinic will usually also do a genetic test (called HLA-B*5701) to see if you are more likely to develop an allergic (hypersensitivity) reaction to the anti-HIV drug abacavir (Ziagen, also in the combination pills Kivexa and Trizivir). For more information on this hypersensitivity reaction, see the NAM booklets Side-effects or Anti-HIV drugs.

Your clinic will also test you for hepatitis B and C, and run tests to look at your blood sugars, the health of your liver and kidneys, and check whether you have anaemia (an iron deficiency in the blood). The results of these tests will help you and your doctor decide the best treatment for you, and when you should start.

Viral load and CD4 tests will tell you about the health of your immune system and if HIV is progressing.

When you start or change a drug combination, a viral load test will be done within the first month, to check that the drugs are working. After this, testing is generally performed every three to four months, although some doctors may perform tests more often to begin with and less frequently once you are established on treatment and doing well. 

If you need to change HIV treatment because your viral load becomes detectable again (see The aim of treatment), your choice of new drugs should be guided by having another resistance test at this stage to see which drugs will work for you.

If you need to change treatment because your current HIV treatment isn’t controlling your viral load, it’s important that you do this in good time to reduce the risk of resistance. How quickly you need to do this will depend on which anti-HIV drugs are taking; your healthcare team will discuss this with you.

Even if you have resistance to several drugs, the range of anti-HIV drugs available now means there will still be options for you. An undetectable viral load is a realistic objective for nearly everyone, including people who have taken a lot of different treatments in the past and have drug-resistant virus. You can find out more about drug resistance and resistance testing later in this booklet.

Once you are on HIV treatment, you will continue to have tests to measure liver and kidney function, and the levels of fat (cholesterol) and sugar in your blood, to assess any effects of the drugs on these systems.

Your HIV care will also involve a number of other routine tests. These will monitor your general health, to see if your treatment is causing any side-effects.

For more information about regular health monitoring, see NAM’s booklet CD4, viral load & other tests.