A 35-year-old woman was admitted with severe low back pain. The patient, who gave birth 5 months ago, was then breastfeeding and presented with postpartum low back pain with increasing severity. Her laboratory results revealed anemia, hypocalcemia, severe vitamin D deficiency, and increase in alkaline phosphatase (ALP) and parathyroid hormone (PTH) levels. Dual energy X-ray absorptiometry (DXA) scan demonstrated lumbar vertebral T and Z scores of -5.1 and -4.4, respectively. The serologic tests for celiac disease (CD) to search underlying malabsorption were positive. Histological analysis of the duodenal biopsy specimen revealed results consistent with the diagnosis of CD. However, because of an absence of gastrointestinal complaints, the diagnosis of subclinical CD could have been made when malabsorption resulted in osteoporosis associated with severe vitamin D deficiency. The initiation of vitamin D therapy showed a significant increase after 6 months at the lumbar vertebra T and Z scores of -0.7 and -0.2, respectively.