The goal of this clinical trial is to evaluate whether a high-intensity loading dose of ergocalciferol (vitamin D2) can normalize blood vitamin D levels more rapidly and safely than standard weekly dosing in patients with newly diagnosed aggressive non-Hodgkin lymphoma. The study will also assess the safety of both dosing strategies.

The main questions it aims to answer are:

• Does a high-intensity loading dose of ergocalciferol lead to faster normalization of serum 25-hydroxyvitamin D levels compared with standard weekly dosing?
• Are there differences in safety and adverse events between the two dosing strategies?

Researchers will compare a high-intensity loading dose regimen of ergocalciferol with a standard weekly dosing regimen to determine differences in vitamin D normalization and safety outcomes.

Participants will:

• Be randomly assigned to receive either a high-intensity loading dose or a standard weekly dose of ergocalciferol (vitamin D2)
• Receive standard first-line immunochemotherapy for aggressive non-Hodgkin lymphoma
• Have blood tests to monitor vitamin D levels, calcium, phosphate, and safety parameters at scheduled visits
• Be followed for treatment response, survival outcomes, and adverse events during and after therapy

Inclusion Criteria:

• Age ≥ 20 years.
• Newly diagnosed aggressive non-Hodgkin lymphoma, confirmed by histopathological examination according to the WHO Classification of Haematolymphoid Tumours, 5th edition, with an indication for standard first-line chemoimmunotherapy
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-3.
• Serum 25-hydroxyvitamin D level < 30 ng/mL within 14 days prior to randomization.
• Adequate organ function to receive full-dose standard chemotherapy.
• Ability to provide written informed consent.

Exclusion Criteria:

• Mild hypercalcemia (corrected Ca > 10.4 mg/dL)
• Hyperphosphatemia (PO4 > 4.5 mg/dL)
• History of urolithiasis associated with hypercalciuria or a diagnosis of primary hyperparathyroidism.
• Chronic kidney disease stage 4 or higher (estimated glomerular filtration rate [eGFR] < 30 mL/min/1.73 m²).
• Inability to take oral medication, active gastrointestinal bleeding, or malabsorption syndrome.
• Pregnancy or breastfeeding.
• Prior systemic therapy for lymphoma.
• Ongoing tumor lysis syndrome requiring urgent treatment.
• Prior use of vitamin D supplements (ergocalciferol or cholecalciferol).

Withdrawal Criteria:

• Development of mild hypercalcemia.
• Development of mild hypophosphatemia.
• Development of hypervitaminosis D.
• Occurrence of severe adverse events (AEs) or side effects for which the investigator considers discontinuation of the study drug necessary for patient safety.
• Investigator's judgment that continued participation may pose a safety risk, such as the occurrence of serious infection, febrile neutropenia, or organ failure.
• Non-adherence to study medication, defined as cumulative vitamin D₂ intake of less than 80% of the expected cumulative dose at the time of serum vitamin D assessment.
• Participant withdrawal of consent to continue participation in the study.

Individual participant data (IPD) will not be shared due to institutional policy and privacy concerns. Only aggregate data may be shared upon reasonable request.