Introduction Vitamin D deficiency is increasingly recognised in neonates especially if born to high risk mothers. Term high-risk newborn infants have higher mean alkaline phosphatase (AP) concentrations than controls, indicating increased bone turnover, although values remain within the normal range. There is little research on vitamin D deficiency in VLBW infants, who are at high risk of bone disease due to osteopenia of prematurity (OP) and potentially maternal or nutritional vitamin D deficiency. We hypothesised that elevated AP levels may predict abnormal vitamin D levels in VLBW infants.

Methods Convalescent, stable VLBW infants admitted to a tertiary referral Neonatal Intensive Care Unit were eligible for inclusion if their AP was >1000 IU in routine “growing” bloods. Vitamin D levels were performed in these infants.

Results 50 VLBW infants had a convalescent AP performed in the first month of life. 32 infants with AP >1000 iu had vitamin D levels sampled of which 10 were in the normal range (>50 nmol/L). AP levels did not correlate with vitamin D, calcium or phosphate levels. Infants with normal vitamin D levels were significantly older than those who were deficient (mean±SD = 76.1±23.2 versus 49.4±25.7 days respectively).

Conclusions Due to the increased risk of OP in VLBW infants early recognition and treatment of vitamin D deficiency is vital. AP, calcium and phosphate are not adequate surrogates for OP and/or vitamin D deficiency. 69% of infants tested for vitamin D were deficient and may suggest that vitamin D levels should be performed in all VLBW at 3–4 weeks of age.