This double-blind randomized placebo-controlled controlled trial will test the hypothesis that administration of high-dose oral vitamin D supplementation to children in Lahore, Pakistan, who are recovering from complicated severe acute malnutrition will safely accelerate weight gain (primary outcome) and enhance neurodevelopment, muscle mass accumulation, resolution of systemic inflammation and antimicrobial immune function (secondary outcomes).

Inclusion Criteria:

• Consent of parent / guardian
• Age 6-59 months at enrolment
• Diagnosis of complicated SAM at the point of hospital admission as defined by the World Health Organisation.
• Medical team managing the child has made the decision to discharge the child from inpatient care

Exclusion Criteria:

• Ingestion of a dose of vitamin D>200,000 IU (5 mg) in the last 3 months
• Known diagnosis of primary hyperparathyroidism or sarcoidosis (i.e. conditions pre-disposing to vitamin D hypersensitivity)
• Known neurodevelopmental disorder (e.g. cerebral palsy)
• HIV infection
• Taking anti-tuberculosis treatment
• Inability to assess child's developmental status at baseline using the Malawi Development Assessment Tool
• Signs of rickets
• Corrected serum calcium concentration >2.65 mmol/L on blood sample taken during the current hospital admission

De-identified IPD will be shared with other researchers subject to terms of Data Transfer Agreement and IRB approval

2 years after completion of the trial