Vitamin D acts more like a hormone than a vitamin: it plays a key role in bone development, immunity, and muscle function. It is produced in the skin through sunlight — but because of modern lifestyles and protective measures, deficiency is still very common in children.

Why Is Deficiency So Common?

  • The low vitamin D content of breast milk
  • Growing up indoors, sunscreens (although necessary, they reduce production)
  • Dark skin tone, winter months
  • Deficiency in the mother during pregnancy

Signs

Mild deficiency is usually silent. As it progresses: delayed teething • late closure of the fontanelle • softening of the bones/bowing of the legs (rickets) • muscle weakness, failure to thrive • frequent infections • bone and muscle pain in older children

Guide to Correct Use

  • Start: From birth, within the first week
  • Dose: 400 IU per day (routine protection); if a deficiency is detected, the physician determines the treatment dose
  • How: Drops directly into the mouth or onto a spoon; if added to formula, make sure all of it is consumed
  • A missed day is not doubled the next day
  • After 1 year of age: continuing all year round, or at least from October to April, is appropriate for most children

Excess vitamin D is also harmful (high-dose ampoules/megadoses should not be used on your own).

To plan it together with iron supplementation: Iron Deficiency Anemia