- Cancer
- Candidiasis see Yeast Infection
- Canker Sores
- Cardiac Diseases see Heart Disease
- Cardiovascular Diseases see Heart Disease
- Carpal Tunnel Syndrome
- Cat-Scratch Disease
- Cataract
- Celexa
- Celiac Disease
- Cellulitis
- Cerebral Aneurysm see Aneurysm
- Cerebral Palsy
- Cerebrovascular Disease see Stroke
- Cervical Cancer
- Cestodes
- Chagas Disease
- Chest Pain
- Chickenpox
- Chigger Bites
- Children's Diseases
- Childrens Skin Rashes
- Chlamydia
- Cholelithiasis see Gallstones
- Cholesterol
- Chronic Bronchitis see Bronchitis
- Chronic Fatigue Syndrome
- Chronic Obstructive Pulmonary Disease see Bronchitis ; Emphysema
- Circulatory System
- Cirrhosis see Liver Disease
- CJD
- Cloning
- Cluster Headache see Headaches
- Cold Sores
- Colitis see Ulcerative Colitis
- Colon Cancer
- Common Cold
- Congenital Heart Disease
- Congestive Heart Failure
- Conjunctivitis see Pink Eye
- Connective Tissue Disorders see Arthritis
- Contact Dermatitis
- COPD see Bronchitis ; Emphysema
- Coronary Heart Disease
- Coxsackie Virus see Hand-Foot-Mouth Disease
- Creutzfeldt-Jakob Disease see CJD
- Crohn's Disease
- Croup
- Cushings Disease
- Cystic fibrosis
- Cystitis see Interstitial Cystitis
- Cytomegalovirus