To Evaluate the Efficacy and Safety of Amorphous Calcium Carbonate in RA Patient With Osteopenia or Osteoporosis

Inclusion Criteria: 1. Men or women ≧45 years of age. 2. Diagnosis of rheumatoid arthritis according to 2010 American College of Rheumatology Guideline (ACR Guideline), with severe osteopenia or osteoporosis. 3. With a DAS28 (Disease Activity Score 28) score ranged from 2.6 to 5.1 at screening visit. 4. With a documented DXA score ≦-2.0 at the lumbar spine or total hip and without compression fracture within the 3 months prior to screening visit. 5. With a FRAX score at least medium risk (major osteoporotic fracture 10-19%, hip fracture 1-3%) at screening visit. 6. Willingness to limit additional vitamin D3 intake to 600 IU per day during the study period. 7. Ability to complete the entire procedure and to comply with study instructions. 8. Will provide completed and signed written informed consents. Exclusion Criteria: 1. History of or current diseases that may interfere serum calcium, such as hypocalcemia, hypercalcemia, hyperparathyroidism, hypoparathyroidism, hyperthyroidism or hypothyroidism, or other metabolic bone disease, from any cause within 1 year prior to screening. 2. Chronic kidney disease with receiving peritoneal dialysis or hemodialysis 3. Known hypersensitivity to any component of the study product. 4. Current treatment with any anti-osteoporotic drug (i.e. bisphosphonates, Denosumab (Prolia), teriparatide (Forteo), Romosozumab (Evenity), Raloxifene (Evista), etc.). 5. Any previous or ongoing clinically significant illness that may interfere with the study conduct, as judged by the investigator. 6. Participation in any other investigational study within 30 days prior to receiving study medication. 7. Any condition that in the opinion of the investigator would jeopardize the evaluation of efficacy or safety.