Key messages
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Giving vitamin D supplements to babies born early (preterm: before 37 weeks of gestation) and with a low birth weight (less than 2500 g) probably reduces the risk of vitamin D deficiency (vitamin D level under 30 nmol/L) and insufficiency (vitamin D level under 50 nmol/L).
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Higher doses (800 IU/day and more) compared to lower doses (200 IU to less than 800 IU/day) of vitamin D in preterm babies probably reduce the likelihood of vitamin D deficiency. However, higher doses may also result in excessive vitamin D levels in some preterm babies.
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Future studies should investigate optimal doses of vitamin D based on babies' weights and report important outcomes such as bone health.
Why is vitamin D important for babies born early (preterm) or with a low birth weight?
Vitamin D helps the body absorb calcium from food, which is vital for bone development and strength. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. This is called Rickets in children. Vitamin D is made in the skin when it is exposed to sunlight. It is also found in fish, meat and other animal-derived foods. Newborn babies may not receive exposure to sunlight, and babies fed human milk may not receive enough vitamin D. Sufficient vitamin D blood levels for babies are 50 nanomoles per litre (50 nmol/L) to 250 nmol/L; 'insufficiency' is under 50 nmol/L and 'deficiency' is under 30 nmol/L. Treatment is with supplements that can be swallowed or given by injection. Too much vitamin D (over 250 nmol/L) can cause unwanted effects, such as high calcium levels in the blood and kidney stones. Recommendations for vitamin D supplementation vary around the world.
What did we want to find out?
We wanted to find out the best dose or duration for giving vitamin D supplements to preterm babies and babies with a low birth weight. We were interested in whether vitamin D supplementation:
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reduces vitamin D deficiency or insufficiency;
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improves bone health;
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causes unwanted effects.
What did we do?
We searched for studies that compared vitamin D supplementation to no supplementation, or higher doses (more than 800 international units (IU)) to lower doses of vitamin D (200 IU to 800 IU) supplementation in preterm babies (born before 37 weeks of gestation) or babies with a low birth weight (less than 2500 g).
We compared and summarised the results of the studies, and rated how confident we are that the results are true and reliable, based on factors, such as study methods and sizes.
What did we find out?
We found 34 studies with 5012 babies.
Main results
Vitamin D supplementation versus no supplementation (11 studies, 1514 preterm babies)
Vitamin D supplementation probably reduces the risk of vitamin D deficiency (benefits 1 in every 4 babies supplemented; 4 studies, 385 babies), and may reduce the risk of vitamin D insufficiency (benefits 1 in every 3 babies supplemented; 4 studies, 385 babies) by the time babies are discharged from hospital. The effects on bone health and bone health blood markers were not reported.
Vitamin D supplementation versus no supplementation (1 study, 2079 near-term, low birthweight babies)
Vitamin D supplementation probably reduces vitamin D deficiency (benefits 1 in every 3 babies supplemented; 453 babies) and probably reduces vitamin D insufficiency (benefits 1 in every 3 babies supplemented; 453 babies) at six months of age. The effects on bone health and bone health blood markers, unhealthily high blood calcium and vitamin D levels were not reported.
Higher-dose (800 IU/day or more) versus lower-dose (200 to 800 IU/day) vitamin D supplementation (25 studies, 1546 preterm babies)
Higher doses of vitamin D probably reduce the risk of vitamin D deficiency (benefits 1 in every 8 babies supplemented; 11 studies; 672 babies), and may reduce the risk of vitamin D insufficiency (benefits 1 in every 4 babies supplemented; 11 studies; 683 babies) more than lower doses of vitamin D. However, higher doses probably lead to unhealthily high vitamin D levels (harms 1 in every 25 babies supplemented; 5 studies; 395 babies). Higher doses of vitamin D in preterm babies may enhance bone health by improving bone health blood markers. However, there may be little to no difference in the appearance of bones with X-rays (7 studies, 447 babies).
What are the limitations of the evidence?
There is not enough information about bone health and unwanted effects, including high blood calcium levels.
We based our judgement on the fact that the evidence is based on a few cases and the parents and assessors in the studies were aware of which treatment they were getting, and a few babies were not followed until the end of the study. We are not confident about other adverse effects from unhealthily high vitamin D levels, and higher blood calcium levels because of few events and small number of participants.
How up to date is this evidence?
The evidence is current to February 2026.
Baca abstrak penuh
Matlamat
To evaluate the benefits and harms of vitamin D (daily cumulative dose ≥ 200 IU) for prevention of vitamin D deficiency in preterm and low birth weight infants.
Kaedah Pencarian
We searched CENTRAL, MEDLINE, Embase, and trials registries, together with reference checking of related studies and included studies. The latest search date was February 2026.
Kesimpulan Pengarang
Vitamin D supplementation (≥ 200 IU/day) in preterm infants probably reduces the risk of vitamin D deficiency and vitamin D insufficiency or deficiency up to discharge/term-corrected age. Vitamin D supplementation in term LBW infants probably reduces the risk of vitamin D deficiency and insufficiency or deficiency up to six months of age. We are uncertain of any other effects on bone health, growth, or morbidities. Higher doses (≥ 800 IU/day) compared to lower doses (< 800 IU/day) probably reduce the risk of vitamin D deficiency and vitamin D insufficiency or deficiency, but probably increase vitamin D excess up to discharge/term-corrected age. Higher versus lower doses in preterm infants may result in little to no difference in radiological evidence of osteopenia of prematurity and bone mineral content, and probably reduces secondary hyperparathyroidism. We are uncertain if a higher dose versus a lower dose in preterm infants affects hypercalcaemia.
Pembiayaan
This Cochrane review had no dedicated funding.
Pendaftaran
Protocol available via DOI 10.1002/14651858.CD011529
