bacteria – single-cell micro-organisms without a nucleus.

base – (also called nucleotide) – the building blocks in DNA that form amino acids. There are four bases represented by the letters A (adenine), T (thymine), C (cytosine) and G (guanine). In RNA the T is replaced by U (uricil).

Genetics, HIV structure and life cycle

baseline – baseline refers to the start of any period being studied. For someone who is HIV positive, their baseline CD4 and viral load counts are the first tests they ever had taken. For someone entering a study, the baseline results refer to their test results at the start of the study. Baseline results for following resistance refers to the results of the first resistance test.

BD (or bid) – a short hand term for medication dosing that means ‘twice-daily’.

See also q12H.

bDNA – branched DNA. A type of viral load test.

benign – not harmful.

BI – budding inhibitor. Class of HIV drug.

bilateral – both sides.

bile duct – a tube that carries bile from the liver to the gallbladder and then to the small intestine biopsy: taking a small sample of body tissue for examination and testing in the laboratory

bilirubin – a liver enzyme. Increased levels of bilirubin lead to a yellowing of the skin or eyes.

Bilirubin and side effects

biopsy – taking a small sample of body tissue for examination and testing in the laboratory.

blip – small, occasional increase in viral load.

blood sugar – glucose in the blood. When carbohydrates are digested they produce glucose, which circulates in the blood and is used by the body as fuel.

BMI (body mass index) – a calculation using  height and weight that is used to decide whether someone is over or under weight.

Online BMI calculator.

boosted-PI – a protease inhibitor taken with an additional dose of ritonavir. The ritonavir boost levels of the protease inhibitor by either increasing the initial drugs levels or reducing how quickly or reducing how quickly it is removed by your body. Ritonavir (itself a protease inhibitor) is currently the only drug used in this way. Other boosters are in development including cobicistat which has no direct anti-HIV activity.

brand name drug – drug supplied under a marketing name. Brand name drugs are usually protected by patents, but some generic drugs also have brand names

buprenorphine – strong pain-killer useful for treating heroin addiction. See also methadone.