One of the rare causes of PTH-independent hypercalcemia can be anabolic oil solution, injected intramuscularly by bodybuilders, along with anabolic hormones, in order to make the muscles more prominent. Here is the clinical report of a 43-year-old patient who used Synthol oil solution at the age of 25–30 years is presented. He had long-term undiagnosed hypercalcemia that manifested with nephrolithiasis and progressing chronic kidney disease (CKD). For the first time hypercalcemia was diagnosed at the age of 37, but left omitted. In 2023 (43 years) the laboratory findings sowed extremely high calcium level (4.26 mmol/l) with decreased PTH and CKD C4. Malignancy hypercalcemia was excluded. With this case, the rare cause of hypercalcemia has been proven – intramuscular oil injection resulting in nephrolithiasis, nephrocalcinosis and CKD. Treatment with glucocorticoids has demonstrated positive effect, similar to the ones of granulomatous diseases and hypercalcemia. The mechanisms of PTH-independent hypercalcemia development and differential diagnosis are currently being discussed. The presented clinical case of a rare cause of hypercalcemia may be useful for doctors of various specialties: endocrinologists, therapists, urologists, dermatologists, etc.