Vitamin B12 Deficiency in Pregnancy: Symptoms, Effects and Treatment

A vitamin B12 deficiency during pregnancy cannot be assessed from a single blood result alone. Symptoms, dietary intake, possible risk factors and the body's ability to absorb vitamin B12 all need to be considered. At the same time, vitamin B12 concentrations can change during pregnancy without necessarily indicating a deficiency that requires treatment.

NUTRILAB MUNICH explains how an abnormal vitamin B12 result can be assessed, which symptoms and risk factors may point towards a deficiency and when further testing or treatment may be appropriate.

Key takeaways

• During pregnancy, an adequate daily vitamin B12 intake is around  4.5 micrograms.
• Whether vitamin B12 deficiency in pregnancy is actually present requires medical assessment based on symptoms, risk factors and suitable laboratory markers.
• The risk is increased in particular with a vegan diet without reliable supplementation, gastrointestinal disorders, previous gastrointestinal surgery and certain medications.
• Possible vitamin B12 deficiency symptoms in pregnancy include persistent fatigue, concentration problems, tingling and numbness.
• A confirmed vitamin B12 deficiency can be treated during pregnancy. Depending on its cause and severity, high-dose oral vitamin B12 or injections may be used.

Low Vitamin B12 During Pregnancy: What Does It Mean?

A low vitamin B12 result during pregnancy does not automatically mean that a true deficiency is present. Measured concentrations can change as pregnancy progresses, which makes it important to understand which marker was tested and what that marker actually reflects.

Total serum vitamin B12 measures all vitamin B12 circulating in the blood. This includes B12 bound to transport proteins that is not immediately available to the body's cells.

Active vitamin B12, also known as holotranscobalamin, reflects the fraction of vitamin B12 that can be taken up by cells. It can therefore provide useful information about how much vitamin B12 is actually available to the body.

For pregnant women with a suspected deficiency, the NICE guideline on vitamin B12 deficiency recommends active vitamin B12 as the initial test. If the result remains inconclusive, additional laboratory markers can help distinguish a true deficiency from changes in blood concentrations associated with pregnancy.

You can find more background information on vitamin B12 at NUTRILAB MUNICH.

Vitamin B12 Deficiency in Pregnancy: Symptoms

The symptoms of vitamin B12 deficiency during pregnancy can vary considerably. A deficiency can affect physical and cognitive performance. More pronounced deficiency may also lead to anaemia and neurological symptoms.

Possible symptoms include:

• persistent or pronounced fatigue
• pale skin, shortness of breath during physical activity or heart palpitations
• concentration and memory problems
• a smooth, red or burning tongue
• tingling or numbness in the hands and feet
• problems with balance or other neurological changes

Neurological symptoms are particularly important during medical assessment because they can occur before typical abnormalities appear in the blood count. The NICE recommendations on recognising vitamin B12 deficiency therefore advise against ruling out deficiency solely because anaemia or enlarged red blood cells are absent.

Causes and Risk Factors for Vitamin B12 Deficiency During Pregnancy

Vitamin B12 from food first needs to be released in the gastrointestinal tract before it can be absorbed in the small intestine. This process depends, among other factors, on intrinsic factor, a protein produced in the stomach.

Disruption at any stage of this process can reduce vitamin B12 absorption. A persistently low dietary intake can also eventually lead to deficiency.

The risk of pregnancy and vitamin B12 deficiency is particularly increased with:

• a vegan diet without reliable vitamin B12 supplementation
• a vegetarian diet containing only small amounts of eggs and dairy products
• autoimmune or atrophic gastritis
• coeliac disease and other conditions that impair nutrient absorption
• previous surgery involving the stomach or small intestine, including gastric bypass or removal of part or all of the stomach
• long-term use of certain medications, including metformin and proton pump inhibitors
• vitamin B12 deficiency that was already present before pregnancy

Because the body can store vitamin B12 for a considerable period of time, a diet-related deficiency often develops gradually.

With a vegetarian diet, vitamin B12 status depends partly on how regularly eggs, milk and dairy products are consumed and whether the body can absorb the vitamin B12 they contain.

How Is Vitamin B12 Deficiency in Pregnancy Diagnosed?

When vitamin B12 deficiency in pregnancy is suspected, the first step is to assess how well the body is actually supplied with vitamin B12.

For pregnant women, the NICE guideline recommends measuring active vitamin B12, or holotranscobalamin. This marker reflects the fraction of circulating vitamin B12 that is available to the body's cells.

If the result falls into an indeterminate range, methylmalonic acid, or MMA, can provide further information. MMA can accumulate when cells do not have enough vitamin B12, so an elevated result may make an existing deficiency more likely.

Homocysteine, an amino acid produced during normal metabolism, can also rise. However, because folate status and other factors influence homocysteine levels, it is generally used as an additional piece of information rather than a standalone marker.

Symptoms, diet, medication use and possible gastrointestinal disorders are also considered. Any vitamin B12 supplements already being taken are relevant because they can affect laboratory results.

What Happens After an Abnormal Vitamin B12 Result?

An abnormal vitamin B12 result should first be assessed in its clinical context. The doctor considers symptoms, possible causes and, when needed, additional laboratory markers.

If a deficiency is confirmed, treatment depends on whether the underlying problem is insufficient intake or impaired absorption and whether neurological symptoms are present.

Is Vitamin B12 Routinely Tested During Pregnancy?

Vitamin B12 status is not part of standard routine testing during pregnancy.

Targeted testing is more likely when symptoms are suggestive of deficiency, when known risk factors such as gastrointestinal disease or a vegan diet are present, or when previous laboratory results have been abnormal.

Effects of Vitamin B12 Deficiency in Pregnancy

Vitamin B12 is involved in the formation of red blood cells and normal functioning of the nervous system. A pronounced deficiency that persists over time can affect maternal health. The developing baby also depends on the mother's vitamin B12 supply.

Effects on the mother

A more severe vitamin B12 deficiency can interfere with normal red blood cell formation and lead to megaloblastic anaemia.

Possible symptoms include fatigue, weakness, shortness of breath during activity and heart palpitations.

Neurological symptoms may also occur. These can include tingling, numbness, reduced sensation in the hands or feet and difficulty walking.

Neurological changes can occur before anaemia becomes visible in a standard blood count. This is why vitamin B12 deficiency anaemia in pregnancy is only one possible manifestation of deficiency.

Effects on the baby

Vitamin B12 contributes to normal cell division and nervous system development.

If the mother is significantly deficient, the amount of vitamin B12 available to the developing baby may also be insufficient.

This relationship continues after birth during breastfeeding. If maternal vitamin B12 deficiency remains severe, a breastfed infant may also develop deficiency, potentially affecting growth and neurological development.

How Much Vitamin B12 Is Needed During Pregnancy?

According to the German Nutrition Society's vitamin B12 reference values, an adequate vitamin B12 intake during pregnancy is around 4.5 micrograms per day. For comparison, the corresponding value is 4.0 micrograms per day for non-pregnant adults and 5.5 micrograms per day during breastfeeding.

Vitamin B12 occurs naturally mainly in animal-derived foods. Sources include fish, meat, eggs, milk and dairy products.

An ovo-lacto-vegetarian diet can provide sufficient vitamin B12 if appropriate foods are consumed regularly and absorption is intact.

With a vegan diet, reliable vitamin B12 supplementation is required. The German Nutrition Society's guidance on vitamin B12 explains that algae, spirulina and fermented plant foods such as sauerkraut are not sufficiently reliable sources for maintaining an adequate vitamin B12 supply.

One food that should not be used to increase vitamin B12 intake during pregnancy is liver. Although liver contains large amounts of vitamin B12, its high vitamin A content makes it unsuitable for targeted intake during pregnancy. The German Federal Institute for Risk Assessment advises pregnant women to avoid liver from all animal species.

Vitamin B12 Dosage and Supplementation During Pregnancy

The German Nutrition Society's reference value of 4.5 micrograms per day refers to an adequate total daily intake of vitamin B12 from food and, where applicable, supplements.

It is not a treatment dose for a diagnosed deficiency.

People following a vegan diet require regular vitamin B12 supplementation. The German Nutrition Society's recommendations for vegan diets specifically emphasise reliable vitamin B12 supplementation.

Someone eating an omnivorous or ovo-lacto-vegetarian diet who already uses a prenatal supplement containing vitamin B12 does not generally require an additional standalone B12 supplement solely because she is pregnant.

If you are looking for a broader prenatal formula, NUTRILAB MUNICH also offers a range of pregnancy supplements.

Why Do Supplements Often Contain Much More Vitamin B12?

Only part of a higher oral vitamin B12 dose is absorbed by the body.

For this reason, supplements can contain considerably more vitamin B12 than the physiological daily requirement. A label stating 100 micrograms, for example, does not mean that 100 micrograms are absorbed or that the body requires 100 micrograms each day.

How Much Vitamin B12 Is in NUTRILAB MUNICH Prenatal Vitamins?

01 femme prenatal for preconception and the first trimester provides 100 micrograms of vitamin B12 per daily dose.

From the second trimester, 02 femme prenatal also provides 100 micrograms of vitamin B12 per daily dose.

This means that when changing from 01 to 02 as pregnancy progresses, the amount of vitamin B12 in the daily dose remains unchanged.

Treatment of Vitamin B12 Deficiency in Pregnancy

With a confirmed deficiency, the amount of vitamin B12 contained in a standard prenatal supplement is generally not sufficient to treat the deficiency.

Depending on the underlying cause and severity, treatment of vitamin B12 deficiency in pregnancy may involve a high-dose oral vitamin B12 preparation or vitamin B12 injections.

The UK Specialist Pharmacy Service guidance on vitamin B12 deficiency treatment during pregnancy lists at least 1 milligram, or 1,000 micrograms, of oral cyanocobalamin per day as a possible therapeutic dose during pregnancy when oral treatment is used.

This is a therapeutic dose and should not be confused with the recommended daily intake for routine nutrition.

If neurological symptoms are also present, treatment should be determined promptly by a doctor. Injectable vitamin B12 may be used depending on the individual findings and the likely cause of the deficiency.

Follow-up After Starting Treatment

During pregnancy, the Specialist Pharmacy Service recommends clinical reassessment approximately one month after starting treatment.

The review focuses particularly on whether symptoms are improving and whether the selected treatment is appropriate for the suspected cause of the deficiency.

Can You Take Too Much Vitamin B12 During Pregnancy?

No conventional tolerable upper intake level has been established for vitamin B12.

However, this does not mean that very high supplemental doses provide additional benefits when there is no medical indication for them.

High therapeutic doses are used specifically to treat a diagnosed deficiency.

Anyone already taking a prenatal vitamin, B-complex or other supplements should therefore check the amounts they contain before adding a separate high-dose vitamin B12 product.

Vitamin B12 Deficiency After Pregnancy and During Breastfeeding

Vitamin B12 remains relevant after birth when the underlying cause of a deficiency continues.

This can apply to a vegan diet, chronic malabsorption or anatomical changes following gastrointestinal surgery.

For breastfeeding women, the German Nutrition Society gives an estimated adequate intake of 5.5 micrograms per day.

With a vegan diet, reliable vitamin B12 supplementation should also continue during breastfeeding.

03 femme postnatal provides 100 micrograms of vitamin B12 per daily dose.

If a vitamin B12 deficiency was already diagnosed during pregnancy, however, a standard postnatal supplement does not automatically replace the prescribed treatment. Continued treatment depends on the cause, laboratory findings and previous therapy.

Vitamin B12 Deficiency Pregnancy: Frequently Asked Questions

Can You Take Vitamin B12 During Pregnancy?

Vitamin B12 can be taken in supplement form during pregnancy and can also be used therapeutically when a deficiency has been diagnosed.

The appropriate dose depends on whether the goal is to maintain an adequate nutritional intake or to correct an existing deficiency.

Does Vitamin B12 Help With Pregnancy Nausea?

Vitamin B12 is not an established treatment for nausea during pregnancy.

Severe or prolonged vomiting can affect overall nutrient intake, but this does not in itself provide a reason to take vitamin B12 specifically for nausea.

Can Vitamin B12 Deficiency Exist Without Anaemia?

Yes. Anaemia does not necessarily develop at the beginning of a vitamin B12 deficiency.

Changes in the blood count may appear later, which means vitamin B12 deficiency can already be present while haemoglobin levels and red blood cell size remain within the normal range. This is also reflected in the NICE guidance on recognising vitamin B12 deficiency.

How Common Is Vitamin B12 Deficiency During Pregnancy?

A systematic review and meta-analysis on vitamin B12 status during pregnancy found pooled estimates of vitamin B12 insufficiency of approximately 21% in the first trimester, 19% in the second trimester and 29% in the third trimester.

These figures describe inadequate vitamin B12 status rather than necessarily a clinically confirmed deficiency.

Vitamin B12 Deficiency and Pregnancy: Conclusion

A vitamin B12 deficiency that becomes apparent during pregnancy may have started before conception.

Because the body can store vitamin B12 for a relatively long period, inadequate intake or impaired absorption can develop gradually before laboratory values or symptoms become noticeable.

Pregnancy may therefore be the point at which an existing gap in vitamin B12 status first becomes visible.

For people with known risk factors, vitamin B12 status is worth considering during preconception planning rather than waiting until pregnancy has already begun.

Note: This article provides general health information and does not replace individual medical advice, diagnosis or treatment.