Secondary anemia has a slow onset and mild symptoms, and the main symptoms include the following: 1. Early common symptoms: fatigue, sleepiness, weakness of limbs, pale skin and mucous membranes; 2. The cardiovascular system may show palpitations, shortness of breath, and in severe cases, heart murmurs; 3. The respiratory system may show shortness of breath and dyspnea; 4. The neurological system symptoms include: dizziness, headache, tinnitus, blurred vision, lack of concentration, drowsiness, irritability. Some elderly patients may have confusion and mental abnormalities; 5. The digestive system mainly shows symptoms: loss of appetite, abdominal organ nausea, acid reflux, etc.; 6. Other symptoms: including dry skin, dry hair, difficulty in wound healing, etc.