Adverse effects of thiazide antihypertensive drugs include hypokalemia, hyponatremia, allergic reactions, and multi-organ functional impairment. 1. Hypokalemia: The main effect of thiazide antihypertensive drugs is to reduce cardiovascular load through sodium excretion. However, sodium excretion will promote potassium excretion, leading to hypokalemia, which can cause weakness, gastrointestinal dysfunction, arrhythmia and other symptoms. 2. Hyponatremia: If the drug is used improperly, it can lead to hyponatremia caused by excessive excretion of sodium ions, which can lead to dizziness, nausea, and in severe cases, there can be consciousness disorder and other manifestations. 3. Allergic reaction: thrombocytopenia, skin rash, urticaria and other manifestations. 4. Multi-organ functional damage: there can be kidney damage, liver damage and other manifestations, mostly secondary to the original existence of the underlying lesions of the liver and kidney. Therefore, thiazide antihypertensive drugs should be taken under the guidance of a doctor, the emergence of serious adverse reactions need to immediately stop the drug and seek medical advice in a timely manner.