Tetany is a group of symptoms associated with increased neuromuscular excitability. Manifest and latent tetany may be distinguished. Manifest (hypocalcaemic) tetany presents with numbness and paresthesia in the areas of the mouth, tongue, hands and feet as well as paroxysmal contractions of the muscles of the face, hands and feet, which may be accompanied by presyncope and syncope. Latent (normocalcaemic) tetany, which is associated with hypomagnesemia or alkalosis, manifests in malaise, depressed mood, pain and irritability. This form of tetany is diagnosed based on typical neurological symptoms such as Chvostek sign, Trousseau sign and Lust sign. Electrolyte disorders that lead to tetany may be caused by imbalanced diet, gastrointestinal, endocrine, nephrological and genetic disorders as well as iatrogenic factors. Manifest tetany seizure requires differentiation from epilepsy. The differential diagnosis should also include angina, migraine and bronchial asthma in the case of manifest tetany as well as other causes of syncope, anxiety and depressive disorders in the case of latent tetany. Tetany is diagnosed based on typical clinical symptoms, laboratory findings and electromyography. If latent form is suspected, special diagnostic tests for tetany are performed. The choice of therapeutic modality depends on the cause of the disease. The treatment of latent tetany involves magnesium and vitamin B6 supplementation. Calcium and magnesium solutions are used in the causative treatment of manifest tetany. It is also worth combining calcium and vitamin D supplementation. The paper discusses three clinical cases: a 15-year-old girl with episodes of syncope, a 17-yer-old girl with fainting, upper limb numbness and impaired vision, and a 16-year-old girl with hand tremor, numbness in the fingers, involuntary muscle contractions in the limbs and palpitations.