This is a randomised, double-blind, double-dummy, multicentre, dose-ranging clinical trial in subjects with vitamin D deficiency or insufficiency. Its general objective is to determine the efficacy and safety of different doses of calcifediol soft gelatin capsules (SGCs) compared to placebo.

Inclusion Criteria:

• Male or female subjects ≥ 18 years of age.
• Evidence of serum 25-OH-D levels < 20 ng/mL or ≤ 10 ng/mL, for each cohort.
• Written informed consent.
• For females of childbearing potential only: willing to perform pregnancy tests, must agree to use highly effective methods of birth control throughout the study.

Exclusion Criteria:

• Subjects receiving any treatment with calcifediol, vitamin D analogues, vitamin complexes or vitamin D supplements.
• Subjects taking drugs that could modify vitamin D levels.
• Subjects taking calcium supplements.
• Uncorrected hypercalcaemia, known hypercalciuria or nephrolithiasis.
• Severe renal impairment.
• Subjects diagnosed with liver or biliary failure, congestive heart failure, malabsorption, primary hyperparathyroidism, hypothyroidism, prolonged immobilisation, sarcoidosis, tuberculosis or other granulomatous diseases or hyperthyroidism.
• Any present or previous malignancy.
• Known contraindications or sensitivities to the use of the IP or any of its components.
• Pregnant woman, breastfeeding woman or woman planning a pregnancy.
• Subject has received an IP within 30 days before the start of the screening or is currently enrolled in an investigational interventional study.
• Any condition that may jeopardise the clinical trial conduct according to the protocol.
• Employees of the investigator or clinical trial site, as well as family members of the employees or the principal investigator.
• Person committed to an institution by virtue of an order issued either by judicial or other authorities.