Vitamin B12 deficiency: treatment during pregnancy

Iram Husain, Regional MI Manager/Pharmacist , London Medicines Information ServicePublished

Intramuscular hydroxocobalamin is the preferred treatment choice for management of clinically relevant vitamin B12 deficiency, including during pregnancy.

Condition Management

It is important to complete an individual risk assessment for your patient and to apply the principles of prescribing during pregnancy when looking at the available information and making treatment decisions. Check to see if a risk assessment has already been completed.

Vitamin B12 (cobalamin) is a water-soluble B vitamin essential for red blood cell formation, neurological function, and DNA synthesis. During pregnancy, vitamin B12 it is essential for normal growth and development of the foetus, in particular neural tube formation and brain development.

Hydroxocobalamin and cyanocobalamin are naturally occurring analogues of vitamin B12 used in the treatment and prophylaxis of vitamin B12 deficiency.


NICE CKS Management of anaemia – vitamin B12 and folate deficiency states that prescribers should seek urgent advice from a haematologist on treating vitamin B12 deficiency anaemia in a pregnant woman.

UK Teratology Information Service (UKTIS) has safety information on the use of vitamin B12 in pregnancy.

Treatment options

There are no UK guidelines regarding the treatment of vitamin B12 deficiency during pregnancy, and no specific dosing recommendations are available. However, treatment should not be withheld for pregnant women who present with symptoms of vitamin B12 deficiency such as megaloblastic anaemia and neurological disorders.

Prescribing in pregnancy should be considered on an individual basis, particularly if there are unusual circumstances, such as complicated obstetric history.


Intramuscular hydroxocobalamin is the standard treatment for clinically significant vitamin B12 deficiency in the UK and when vitamin B12 injection is prescribed, hydroxocobalamin injection will be supplied.

When a vitamin B12 deficiency state exists AND vitamin B12 is clinically indicated for the management of maternal illness in pregnancy, treat with intramuscular hydroxocobalamin.

Dosing regimes

The UK recommendations for the treatment of pernicious anaemia and other macrocytic anaemias due to vitamin B12 deficiency in the general population can also be considered for use in pregnancy.

Without neurological involvement
  • Intramuscular hydroxocobalamin: 1 mg three times a week for 2 weeks initially, then 1 mg every 2 to 3 months thereafter (if the deficiency is not diet related).
With neurological involvement
  • Intramuscular hydroxocobalamin: 1mg daily on alternate days until no further improvement, then 1mg every 2 months.

Monitoring in pregnancy

The use of vitamin B12 at any stage in pregnancy is not regarded as grounds for additional foetal monitoring.


The NHS considers cyanocobalamin less suitable for prescribing. It is available in oral form but would not be considered for use in clinically significant vitamin B12 deficiency.

Hydroxocobalamin has replaced cyanocobalamin as vitamin B12 form of choice.

Pregnancy outcome information

UKTIS provides an overview of the use of vitamin B12 in pregnancy.

Patient information

UKTIS has corresponding BUMPS patient information on the use of vitamin B12 in pregnancy.

NHS Medicines A-Z provides summary statements for the use of specific supplements in pregnancy: hydroxocobalamin, cyanocobalamin.