The full name of BMD is bone mineral density, which is an important indicator of bone strength, expressed in grams per cubic centimeter, and is an absolute value. In the clinical use of bone mineral density value due to the different absolute values of different bone mineral density testers, the T value is usually used to determine whether the bone mineral density is normal. The most commonly used test is the dual energy X-ray absorptiometry (DEXA), which is a relative value with a normal reference value between -1 and +1. A T value is abnormal when it is below -2.5. Bone mineral density, an important marker of bone quality, reflects the degree of osteoporosis and is an important basis for predicting fracture risk. Bone density test results include mean and standard values. The average value is the actual test result. The standard value is pre-stored in the computer, which consists of two parts: standard value ± standard deviation. The standard values have different values according to the combination of gender and age, i.e., they are divided into two series groups according to male and female gender, and subgrouped according to age at the same time. The difference between the mean and the standard value is determined by comparing the T value with the standard deviation in the standard value: a T value between -1 and +1 is normal; a T value between -1 and -2.5 is reduced bone mass; a T value below -2.5 is osteoporosis. Osteoporosis manifests as: (1) Pain: the most common symptom of primary osteoporosis, with low back pain being the most common, accounting for 70% to 80% of the patients with pain. The pain spreads along the spine to both sides, decreases when supine or sitting, increases when posterior extension or prolonged standing or sitting, and worsens when bending, coughing, and bowel movements. (2) Shortening of body length and hunchback: mostly occurs after pain. The anterior part of the vertebrae of the spine is heavily weighted and easily compressed and deformed, causing the spine to tilt forward and forming a hunchback. As we age, osteoporosis increases and the curvature of the hunchback increases. (3) Fracture: It is the most common and serious complication of degenerative osteoporosis. Fractures are common in the spine, wrist and hip. (4) Decreased respiratory function: compression fractures of the thoracic and lumbar spine, backward curvature of the spine, and thoracic deformity can significantly reduce lung capacity and maximum air exchange, and patients can often experience chest tightness, shortness of breath, and dyspnea. Low bone density, after the occurrence of osteoporosis, effective measures are as follows: 1. Exercise: In adulthood, many types of exercise help maintain bone mass. Menopausal women adhere to 3 hours of exercise per week, the overall calcium increase. But those who exercise excessively to cause amenorrhea, bone loss is accelerated instead. Exercise also improves sensitivity as well as balance, encouraging patients with osteoporosis to be as active as possible. 2, nutrition: good nutrition is important for the prevention of osteoporosis, including adequate amounts of calcium, vitamin D, vitamin C and protein. From childhood onwards, the daily diet should have adequate calcium intake, which affects the acquisition of peak bone mass. European and American scholars advocate calcium intake of 800-1000mg for adults, 1000-1500mg per day for postmenopausal women, and 1500mg/day for men after 65 years of age and other patients with risk factors for osteoporosis. The intake of vitamin D is 400 to 800 U/day. 3.Prevention of falls: The chances of falls in patients with osteoporosis should be minimized to reduce osteoporotic fractures. 4.Medication: Effective drug therapy can stop and treat osteoporosis, including estrogen replacement therapy, calcitonin, selective estrogen receptor modulators, and diphosphonates, which can stop bone resorption but have particularly small effects on bone formation. The drugs used to treat and stop the progression of osteoporosis are divided into two main groups: the first group is the drugs that inhibit bone resorption, including calcium, vitamin D and active vitamin D, calcitonin, diphosphonates, estrogens, and isoflavones; the second group is the drugs that promote bone formation, including fluoride, anabolic steroids, parathyroid hormone, and isoflavones. Remember, the above medications must be administered under the guidance of a professional physician after the completion of a bone density test.