Although tooth extraction is a minor surgery, there are some people who cannot have their teeth extracted temporarily. 1. Hematological diseases: People who can cause reduced blood coagulation and more than postoperative bleeding, such as hemophilia, leukemia, aplastic anemia, thrombocytopenic purple disease and scurvy, should avoid tooth extraction. 2. Liver disease: tooth extraction should be postponed for those with acute hepatitis or severe liver function damage because such liver disease can cause more than postoperative bleeding due to lack of prothrombin and fibrin or the inability of the liver to use vitamin K to synthesize the relevant coagulation factors, and tooth extraction must be postponed until the disease improves. For chronic hepatitis, tooth extraction is possible for those with no significant damage to liver function, but prothrombin time measurement should be done before surgery. To prevent postoperative bleeding, hemostatic drugs such as vitamin K and hemostatin should be used after tooth extraction. 3. Renal disease: Those with severe renal impairment cannot have their teeth extracted to avoid renal failure. In general, for those with mild kidney disease, antibiotics should be injected before tooth extraction to prevent temporary bacteraemia caused by tooth extraction from prompting an acute attack of kidney disease. 4. Diabetes: Diabetic patients are prone to infection after surgery due to reduced resistance. For those who are seriously ill, tooth extraction should be postponed, and for those who must be extracted, a consultation with an internist should be requested to control blood sugar not to be too high before tooth extraction (fasting blood sugar in the early morning should not exceed 6.8 mmol/l, i.e. 160 mg%). Antibiotics should be used before and after tooth extraction surgery to prevent complications of infection. 5. Hyperthyroidism: Such patients may suffer from sudden aggravation of thyroid poisoning caused by infection, anxiety and various surgeries, i.e., thyroid crisis; in severe cases, it can rapidly cause failure or even death, so it is not advisable to extract teeth rashly. If tooth extraction is necessary, a detailed examination should be made, and the basal metabolic rate should be below 20%, and the pulse rate should be below 100 beats per minute. Epinephrine should not be added to the anesthetic, and anti-inflammatory drugs should be used after the operation. 6. Organic or functional mental or neurological disorders: Patients with such diseases should consider the possibility of causing disease attacks during and after surgery, so they should be extracted after consultation and treatment by a neurologist, and sedatives should be taken before surgery. 7. Other diseases: For acute infectious diseases, pernicious anemia, severe tuberculosis, malnutrition, and excessive fatigue can reduce the body’s resistance and slow down the healing of wounds, and are also prone to co-infection, so tooth extraction should be postponed. In conclusion, patients suffering from internal diseases must tell the doctor about their conditions before tooth extraction so that the doctor can handle them accordingly.