Safety of vitamin D supplementation in children: a massive vitamin D overdose with no apparent hypercalcaemia

Abstract

Aim To report the highest recorded vitamin D overdose in a child. This case is also unique in that there was no associated hypercalcaemia and the child did not require treatment. Methods A 12-year-old girl of Somali descent was followed up in neurodisability clinic for complex epilepsy and a progressive movement disorder manifesting as ataxia and progressive dystonia. Her diet contained a normal amount of calcium. She was on regular lamotrigine for seizure control. She was found to be vitamin D deficient with a total 25 hydroxyvitamin D level of 32 nmol/l. Her general practitioner was asked to prescribe vitamin D supplements. In error, she was prescribed and dispensed 100,000 units of colecalciferol a day. She took the prescribed dose over a period of at least 3 months – ingesting at least 150 capsules of 50,000 units each or a total of 7.5 million units. This error came to light when her serum total 25 hydroxyvitamin D level was measured six months later to check whether she had taken enough vitamin D. A literature search was conducted to look for cases of vitamin D intoxication. Results This patient9s peak measured serum 25 hydroxyvitamin D level was 671 nmol/L with corresponding serum corrected calcium of 2.44 mmol/L. Her 1,25 dihydroxyvitamin D level a month after this was 254 pmol/L (reference range 40-150) and her parathyroid hormone level was 5.5 pmol/L, which was normal. A renal ultrasound showed no evidence of nephrocalcinosis. She remained asymptomatic and well throughout. The literature search found no reports of vitamin D overdose of higher magnitude in a child and no relationship between size of overdose and serum calcium. All cases of overdose, from 900,000 to 4.5 million units of vitamin D, were associated with hypercalcaemia, which ranged from 3-4.6 mmol/L and required treatment. Conclusions Clinicians are gaining awareness of the need for vitamin D supplementation. Many medicines in children are prescribed off-licence. It is the responsibility of physicians and pharmacists to ensure they take extra care when prescribing unlicensed medications. Recommendations for vitamin D supplementation, including indications and doses should be made widely available, e.g. in the BNF (British National Formulary).