National Institute for Health and Care Excellence (NICE) guidelines, UK [65]

400 IU

Institute of Medicines (IOM) [58]

600 IU

Endocrine Society [32]

1500 - 2000 IU

Canadian Pediatric Society [64]

2000 IU

American Congress of Obstetricians & Gynecologists (ACOG) [61]

1000 - 2000 IU