Find out what causes dandruff, what you can do to get rid of it and when to get medical advice.
Decongestants are medicines that can provide short-term relief for a blocked or stuffy nose (nasal congestion). Find out about the different types and who can take them.
A dental abscess is a collection of pus that can form inside the teeth, in the gums, or in the bone that holds the teeth in place. It’s caused by a bacterial infection.
Read about the two types of dentures – complete dentures and partial dentures. Find out how dentures are fitted, how to care for your dentures and when to see your dentist.
Find out more about dyspraxia, which is a common disorder that affects movement and co-ordination. Read about the symptoms, causes and treatments for dyspraxia, and find out when to get medical help.
Developmental dysplasia of the hip (DDH) is a condition where the ball and socket joint of the hips does not properly form in babies and young children.
Read about diabetes, a lifelong condition that causes a person's blood sugar level to become too high.
Find out about diabetic eye screening, which can help spot eye problems caused by diabetes before they affect your sight.
Read about diabetic ketoacidosis (DKA), a serious complication of diabetes, including why it happens, what the symptoms are and how to prevent it.
Find out about DiGeorge syndrome (22q11 deletion), including why it happens and what problems it can cause.
Read about the symptoms of a dislocated kneecap, what to do and how long it usually takes to recover.
Find out about dislocated shoulder, including how a dislocation happens, how to tell if your shoulder is dislocated, what to do, plus treatment and recovery.
Find out about differences in sex development (DSDs), a group of rare conditions where the reproductive organs and genitals don't develop as expected. Some people prefer to use the term intersex.
Dissociative disorders are a group of conditions where you may feel disconnected from reality. Find out more, including where to get help.
Find out about diverticular disease and diverticulitis, related digestive conditions that affect the large intestine (bowel).
Dizziness is a common symptom that’s not usually a sign of anything serious, but its cause should be investigated by a doctor.
Read about dry mouth, including what causes it and things you can do to help ease it yourself.
Information and advice about dysarthria – difficulty speaking caused by problems controlling the muscles used in speech.
Find out about dysentery, including the symptoms, when to see a GP, treatment, how to reduce your risk of getting it and how to avoid passing it on to others.
Read about deafblindness, a condition in which a person has a combination of sight and hearing difficulties that affect their everyday activities.
Read about DVT (deep vein thrombosis), including how to tell if you have a DVT and treatment. Also, what causes DVT and how to reduce your chances of getting it.
Dehydration occurs when your body loses more fluid than you take in.
Find out about a type of dementia called dementia with Lewy bodies, including what the symptoms are, how it's treated and what the outlook is.
Find out what dengue is, how it's spread, where it's found, what the symptoms are, and how to avoid it.
Read about developmental co-ordination disorder (DCD), also known as dyspraxia, a condition that affects physical co-ordination.
Diabetes insipidus is a rare condition where you produce a large amount of urine and often feel thirsty.
Diabetic retinopathy is a complication of diabetes, caused by high blood sugar levels damaging the back of the eye (retina). It can cause blindness if left undiagnosed and untreated.
Dialysis is a procedure to remove waste products and excess fluid from the blood when the kidneys stop working properly. It often involves diverting blood to a machine to be cleaned.
Diphtheria is a potentially fatal contagious bacterial infection that mainly affects the nose and throat, and sometimes the skin. It is very rare in England.
Read about discoid eczema (nummular or discoid dermatitis), a long-term (chronic) skin condition that causes the skin to become itchy, reddened, dry and cracked
A disorder of consciousness, or impaired consciousness, is a state where consciousness is affected by an injury to the brain.
Double vision (medically known as diplopia) is where you see 2 images of a single object either some or all of the time.
Down's syndrome is when you're born with an extra chromosome.
Dry eye syndrome, or dry eye disease, is a common condition that occurs when the eyes do not make enough tears, or the tears evaporate too quickly.
Read about Dupuytren's contracture (Dupuytren's disease), which affects the hands and fingers and causes 1 or more fingers to bend into the palm of the hand.
Read about dyslexia, a common type of learning difficulty that can cause problems with reading, writing and spelling.
Dystonia is the name for uncontrolled and sometimes painful muscle movements (spasms). Find out about the main symptoms, types and treatments.
Read about a detached retina, which is where the thin layer at the back of the eye (retina) becomes loose from the back of the eye. Find out what the symptoms are, what causes it and how it's treated.
Dysphagia is the medical term for having difficulty swallowing.
Read our guide on dementia, which covers possible causes, symptoms and treatments, plus guidance for family and friends on living with dementia.
Diarrhoea and vomiting are common in adults, children and babies. Find out how to treat and avoid spreading them, and when to get medical help.
DNACPR means if your heart or breathing stops your healthcare team will not try to restart it. A DNACPR decision is made by you and/or your doctor or healthcare team.