General considerations

It is important to complete an individual risk assessment for your patient and to apply the principles of prescribing in breastfeeding when looking at the available information and making treatment decisions.

Forms of vitamin D

Vitamin D is available in many different forms. Colecalciferol (vitamin D3) or ergocalciferol (vitamin D2) are the two main vitamin D compounds used for the treatment and prevention of vitamin D deficiency. General guidance on the Safety considerations when using Vitamin D is available.

This article advises on the use of colecalciferol and ergocalciferol during breastfeeding. For other forms of vitamin D (including alfacalcidol and calcitriol), please contact our specialist service for further advice.

Terms to describe the vitamin D doses

This article refers to vitamin D dosing as the following:

• prevention/supplement doses (usually 400 units daily).
• maintenance doses (up to 4000 units daily) where treatment of vitamin D deficiency is not considered urgent or maintenance therapy is required.
• loading doses (above 4000 units daily) where the treatment of vitamin D may require rapid correction.

Loading doses will usually not exceed a cumulative total dose of 300,000 units divided into daily or weekly dosing over 6–10 weeks. Loading doses can be administered as various dosing schedules; examples include 50,000 units once weekly for 6 weeks, or 4000 units daily for 10 weeks.

Recommendations in breastfeeding

National guidance recommends that all those who are breastfeeding should receive a supplement of 340 to 400 units daily of vitamin D.

Long term maintenance doses up to 4000 units daily can be used during breastfeeding and do not require any infant monitoring.

Loading doses are acceptable during breastfeeding with infant monitoring as a precaution, although side effects would not be expected.

Regimens totalling more than 300,000 units, which may include a treatment course longer than 10 weeks or 300,000 units given in less than 6 weeks, can still be considered during breastfeeding, but with more caution. Contact our specialist service for further advice.

Evidence

There is a lot of evidence about the use of the usual treatment doses of vitamin D during breastfeeding. However, evidence for use of loading doses totalling more than 300,000 units is very limited, often relying on single case reports.

The amount that gets across into breast milk, and levels reported in infant serum, is very variable. There is also a huge range of dosing schedules and different administration routes that can be used, and not all have been studied.

Therefore, the likely vitamin D concentrations in breast milk can be difficult to predict for any given scenario.

Natural Vitamin D in breast milk

Vitamin D is a natural component of breast milk, with colecalciferol, ergocalciferol, and their metabolites, being the primary forms present. The amount is related to maternal plasma levels. However, breast milk contains insufficient vitamin D for breastfed infants to maintain the minimum required levels.

Doses

Vitamin D can be used in breastfeeding at all dosing schedules; higher doses require infant monitoring.

Prevention/supplement dose recommended

The Scientific Advisory Committee on Nutrition (SACN) recommends vitamin D supplementation for all those who are breastfeeding. The recommended dose is 340 to 400 units daily.

Vitamin D is synthesised through skin exposed to the sun. It can also be obtained from some foods such as oily fish and fortified cereals. However, in the UK these generally do not provide adequate vitamin D levels, therefore daily supplementation is recommended.

Maintenance doses

Doses up to 4000 units daily are considered compatible with breastfeeding, with no specific infant monitoring necessary.

Loading doses for rapid treatment

Breastfeeding can continue as normal when loading doses are required for rapid treatment of vitamin D deficiency, although infant monitoring is required.

There is no upper limit of vitamin D dosing during breastfeeding, but the risk of infant hypercalcemia becomes greater as the dose gets higher. Therefore, it is recommended that loading dose regimens totalling more than a cumulative dose of 300,000 units, which may include a treatment course longer than 10 weeks, or 300,000 units given in less than 6 weeks, need additional monitoring of the infant. This may include checking infant calcium levels. Contact our specialist service for further advice.

The very extended half-life of vitamin D also needs to be considered, since the effects of vitamin D exposure for the infant could continue well beyond the maternal treatment period.

The evidence regarding higher doses is limited during breastfeeding, but those which have been used are reassuring. Doses of 150,000 units given as a single dose, 60,000 units daily for 10 days, 120,000 units once monthly for 12 months have not reported any adverse effects in the breastfed infants. In a case study, a mother was given 100,000 units daily throughout pregnancy and then while breastfeeding, due to thyroid parathyroidectomy. At 11 days old, the infant was found to have mild asymptomatic hypercalcemia.

Infant Vitamin D Supplementation

Breast milk does not contain enough vitamin D for the exclusively breastfed infant. When there is vitamin D deficiency, it is highly likely that the infant will also have inadequate vitamin D levels.

The Scientific Advisory Committee on Nutrition (SACN) recommends that breastfed infants should take 340 to 400units of vitamin D supplement daily unless they are also consuming over 500mL of infant formula a day (since this is already fortified).

Breast milk levels

It is sometimes questioned whether higher maternal vitamin D doses may provide enough vitamin D in the breast milk to meet the requirements of the infant, therefore avoiding the need for direct infant supplementation.

However, direct infant supplementation is thought to be superior to maternal supplementation via breast milk.

The level of the vitamin D that the infant will receive via breast milk is dependent on the maternal vitamin D status, maternal vitamin D dose, treatment course length, and the amount of milk being consumed, so can be variable.

There is some limited evidence which has suggested that mothers taking 4000–6400 units of vitamin D daily could achieve sufficient breast milk levels for their infants to receive the recommended daily dose. Other studies have suggested that doses of 8500 units daily would be required. However, this has been based on extrapolation; with no direct evidence to show the actual effect of higher maternal dosing on infant vitamin D levels.

Advice

The infant should continue to be supplemented directly, with 340 to 400 units daily of vitamin D, regardless of the maternal vitamin D dose. This includes any dose used for prevention/supplementation, maintenance or loading doses. This will guarantee the infant is achieving their daily requirement.

If loading dose regimens total more 300,000 units, which may include a treatment course longer than 10 weeks, or 300,000 units given in less than 6 weeks, contact our specialist service for further advice regarding infant supplementation.

Vitamin D toxicity

The vitamin D milk level which is thought to cause infant toxicity is around 4000 units/litre, although this is poorly documented and it could be a lot higher than this. A maternal dose of 6400 units daily has resulted in a milk level of 873 units/litre. Therefore, when direct infant supplementation of 340 to 400 units is also given, this would still not be achieving levels that would be considered toxic.

Infant monitoring

Side effects are generally not expected in breastfed infants, and therefore no specific infant monitoring is required when maintenance doses up to 4000 units daily are being used. However, as a precaution, monitor the infant for any unusual sign or symptoms.

When loading doses are being used, the infant should be monitored for signs of hypercalcaemia as a precaution, including increased wet nappies, lethargy, gastro-intestinal disturbances, and changes in feeding. The infant should also be monitored for irritability and skin reactions.

Infant calcium levels should be monitored if:

• hypercalcaemia is suspected due to infant symptoms
• loading doses above 300,000 units are required, which may include treatment courses longer than 10 weeks
• loading doses totalling 300,000 units are given in less than 6 weeks.

Contact our specialist service for further advice.

Patient information

The NHS website provides advice for patients on the use of specific medicines in breastfeeding.

Contact us

Get in touch with the UK Drugs In Lactation Advisory Service (UKDILAS), our specialist breastfeeding medicines advice service if you need support in the following situations:

• a higher dose or course length is being considered
• you need further advice
• the medicine in question is not included here
• the infant is unwell or premature
• multiple medicines are being taken

About our recommendations

Recommendations are based on published evidence where available. However, evidence is generally very poor and limited, and can require professional interpretation. Assessments are often based on reviewing case reports which can be conflicting and lack detail.

If there is no published clinical evidence, assessments are based on: pharmacodynamic and pharmacokinetic principles, extrapolation from similar drugs, risk assessment of normal clinical use, expert advice, and unpublished data. Simulated data is now increasingly being used due to the ethical difficulties around gathering good quality evidence in this area.

Bibliography

Full referencing is available on request.

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