DAA (direct acting antiviral) – new hepatitis C drugs that work directly against the hepatitis C virus (HCV).

Since 2014, the following DAAs and fixed dose combinations have been approved – and more are in development. Links are to the EMA website for information on each DAA.

Previously, HCV was treated with pegylated interferon (PEG-IFN) plus ribavirin (RBV).

Even though HCV guidelines now only recommend oral DAA treatment, the high price of these medicines means that in many countries they are only available to people who have advanced liver damage.

decimal fraction – a fraction turned into a number by dividing the top part by the bottom part. For example, the decimal fraction for 3/5 is 0.6.

DEXA – a non-invasive scan that can measure the percentage of different body areas (whole body, trunk, right leg etc) that are muscle or fat. DEXA scans cannot determine if this is central fat (visceral adipose tissue, VAT) or sub-cutaneous fat (under the skin).

DEXA scan also can measure bone density and is used to monitor risk of osteopenia and osteoporosis.

diabetes – when the body either does not produce enough insulin (a hormone that helps the body turn sugar into energy) or is not responding to insulin (insulin resistance). There are two main types of diabetes and they have different mechanisms and treatments.

Type-1 is mainly reported in children but can also occur in adults and is linked to genetic risks.

Type-2 is mainly reported in adults (but increasingly in children) and is more commonly related to lifestyle factors including diet, exercise, weight/BMI. Some medications can increase the risk of Type-2 diabetes.

Diabetes can also be a side effect, including from some early HIV drugs, and this is sometimes referred to as a third type. This is because it was primarily caused as a side effect, rather than being driven by either lifestyle factors or genetics.

Other commonly-used drugs that can affect glucose regulation include corticosteroids and some drugs to reduce high blood pressure, or lipids.

diagnosis – identifying the cause of an illness.

diarrhoea – when stools (faeces) is less than firm. This can range from loose to being very watery. As a medical condition it is usually also associated with needing to go to the toilet more frequently.

For example, this is commonly defined as three or more liquid/watery faeces over 24 hour period.

See this information from the i-Base guide to side effects for ways to manage and treat diarrhoea.

Direct acting antiviral – See DAA.

DNA – an abbreviation for the scientific word for genes and genetic material. It is the abbreviation for deoxyribonucleic acid. See RNA.

DOT (directly observed therapy) – where a nurse or other healthcare worker observes or supervises someone take medicine.

dronabinol – medicine made from the active ingredient in marijuana. Dronabinol is approved in the US but is no longer available in the UK.

drug resistant (HIV) – HIV that is harder to treat because of genetic changes.

drug resistant mutation – a mutation or change that occurs in the HIV genome that reduces a drugs ability to work.

dual therapy – using 2 drugs together.

duration – how long in time.

duration of ruptured membranes – time between when the mother’s waters break and the actual delivery.

dyspepsia – a range of symptoms related to digestion problems that can include pain, nausea, heart burn. vomiting and pain in the stomach or upper intestine.

dyspnoea – medical term for symptoms related to difficulty breathing, shortness or breath.