A very small number of people taking the anti-HIV drug tenofovir (Viread, also in the combination pills Truvada and Atripla) and possibly protease inhibitors have developed bone problems.

Nearly always, they also had other risk factors for bone problems. Your doctor will do blood tests to monitor the health of your bones. These tests are likely to be particularly important if you have other risk factors for bone problems such as family history, diet, age, sex, smoking and not exercising.

Lactic acidosis is a serious side-effect of some drugs from the NRTI class. The use of the drugs most associated with it, d4T and ddI, is now avoided as much as possible. But it can be a very rare side-effect of 3TC, abacavir and FTC.

The term lactic acidosis is used to describe high levels of a substance called lactate in the blood. Lactate is a by-product of the processing of sugar within the body.

Initial signs and symptoms of lactic acidosis include general gastrointestinal symptoms such as nausea (feeling sick), vomiting, bloating, abdominal pain and lack of appetite, feeling generally unwell, and difficulty in breathing. Of course, these symptoms can also occur for many other reasons, but it makes good sense to tell your doctor as soon as possible if you develop any of these symptoms. In people who have lactic acidosis, the liver may be swollen and tender and liver enzymes, which are measured by a liver function test, may be abnormally high. Other signs which may be detected on laboratory tests include low bicarbonate, raised lactate, and deteriorating kidney function.

Your routine HIV care will include blood tests that can show if you have a risk of developing this very rare side-effect.

Changing HIV treatment is often the best way of dealing with lactic acidosis.

Pancreatitis is inflammation of the pancreas and is a very rare side-effect of drugs from the NRTI class. The NRTI most associated with pancreatitis is ddI, and the use of this drug is now avoided as much as possible.

People who have other risk factors for pancreatitis, particularly heavy drinking and a very low CD4 cell count, are at higher risk of getting pancreatitis if they are taking ddI. In addition, people who are receiving treatment for HIV including ddI, and treatment for hepatitis C at the same time, seem to be at a higher risk of developing the condition.

Symptoms include feeling sick, being sick, and pain, which can be very severe in the area where the ribs join in the middle of the chest. The stomach can also be very tender and painful to the touch. If the pancreas stops working properly, food might not be digested properly and this can cause weight loss and diarrhoea, which is pale and very smelly due to undigested fat.

Your doctor will do regular blood tests to check if you have a risk of developing pancreatitis.