- Salivary gland cancer
- Sarcoidosis
- Sarcoma (bone cancer)
- SARS
- Scabies
- Scarlet fever
- Scars
- Schistosomiasis
- Schizophrenia
- Sciatica
- Scleroderma
- Scoliosis
- Scurvy
- Seasonal affective disorder (SAD)
- Seasonal allergic rhinitis
- Seasonal flu
- Selective serotonin reuptake inhibitors
- Self-harm
- Sepsis
- Septic shock
- Septicaemia
- Sex change
- Sexual health clinics
- Sexually transmitted infections (STIs)
- Shigella
- Shin splints
- Shingles
- Shingles vaccination
- Short-sightedness
- Shortness of breath
- Shoulder dislocation
- Shoulder pain
- Sick building syndrome
- Sickle-cell anaemia
- Sickness and diarrhoea in children
- Sickness in children and babies
- Singultus
- Sinus headache
- Sinusitis
- Sjogren's syndrome
- Skin cancer (melanoma)
- Skin cancer (non-melanoma)
- Skin tags
- Slapped cheek syndrome
- Sleep apnoea
- Sleep paralysis
- Sleepwalking
- Slipped disc
- Small bowel transplant
- Smelly feet (bromodosis)
- Smoking (quitting)
- Snake bites
- Snoring
- Soft tissue sarcoma
- Solvent abuse
- Sore and dry lips
- Sore throat
- Spina bifida
- Spinal muscular atrophy
- Sports injuries
- Sprains and strains
- Squint
- SSRIs (selective serotonin reuptake inhibitors)
- Stammering
- Staphylococcal infections
- Statins
- Stem cell transplant
- Sterilisation
- Stiff neck
- Stillbirth
- Stings, insect
- Stings, marine creatures
- Stings, sea creatures
- STIs
- Stoma
- Stomach ache
- Stomach cancer
- Stomach cramps
- Stomach ulcer
- Strawberry mark
- Strep throat
- Streptococcal infections
- Stress
- Stress incontinence
- Stretch marks
- Stria
- Stroke
- Stroke, mini
- Stuttering
- Stye
- Subarachnoid haemorrhage
- Subcutaneous sarcoidosis
- Subdural haematoma
- Sudden infant death syndrome (SIDS)
- Suicide
- Sunburn
- Supraventricular tachycardia
- Surgery, going into hospital
- Sweat rash
- Sweating, excessive (hyperhidrosis)
- Swelling or lump
- Swimmer's ear
- Swine flu
- Swollen glands
- Syphilis
- Systemic lupus erythematosus