Weak breath may be caused by severe malnutrition, hypoglycemia, heart failure, lung lesions, neuromuscular disease, etc. 1. severe malnutrition: long-term lack of nutrient intake, gastrointestinal tract digestion and absorption dysfunction, advanced malignant tumors and other people seriously lack of nutrition, the body’s tissues and cells are low-functioning, and thus the breath will be weak. 2. Hypoglycemia: when the blood sugar level is lower than normal, the tissue cells of the body lack energy supply, leading to dysfunction of respiratory muscles and other important tissues, so the breath will be weak. 3. Heart failure: ventricular systolic-diastolic dysfunction leads to stagnation in the pulmonary circulation, and pulmonary ventilation and hyperventilation are inhibited, so the breath will be weak. 4. Lung disease: severe asthma, acute exacerbation of chronic obstructive pulmonary disease (COPD), severe pneumonia, advanced lung cancer, pneumothorax and other lung diseases, or caused by airway narrowing and spasm leading to impaired lung ventilation, or cause lung hyperventilation, and thus weak breath. 5. Neuromuscular disease: Guillain-Barré syndrome, myasthenia gravis, hypokalemia, organophosphorus poisoning and other diseases lead to nerve dysfunction of the innervating respiratory muscles or signaling disorders at the neuromuscular junctions, so the breath will be weak. Weakness of breath may be related to a variety of factors, it is recommended to consult a doctor for a definitive diagnosis.