Brief answer: Vitamin B12 is essential for cell formation, DNA synthesis, and nerve function, and it is involved with folate in the body's homocysteine metabolism. Research suggests a connection between good B12 status and fertility in both women and men, but the evidence is limited, and causal relationships are not established. Deficiency is rare with a balanced diet including animal products; vegans should take supplements.
What does vitamin B12 do in the body?
Vitamin B12 (cobalamin) is needed for the formation of red blood cells, for DNA synthesis, and for the function of the nervous system. Along with folate, B12 participates in the metabolism of the amino acid homocysteine – a process that is central when cells divide rapidly, for example, during the formation of germ cells and early in a pregnancy. According to the Swedish Food Agency, B12 is found almost exclusively in animal foods such as meat, fish, seafood, eggs, and dairy products, and the recommended daily intake for adults is around 4 micrograms.
B12 and female fertility
Studies that have compiled the role of nutrients in reduced fertility have noted that low levels of B12 may occur more frequently in women with fertility difficulties, and that B12, along with folate, may be important for egg quality and early embryonic development. It should be emphasized that much of this is based on observational studies with limited data – they show correlations, not that B12 supplements themselves improve the chance of becoming pregnant. With a varied diet, deficiency is uncommon.
B12 and male fertility
In men, research has also investigated the link between B12, folate, and sperm quality. Some studies suggest that good B12 status may be associated with better sperm parameters, but the results are mixed and the evidence is insufficient to draw firm conclusions. As part of a nutritious diet and healthy lifestyle, it is reasonable to ensure sufficient B12 intake, but B12 should not be considered a treatment for reduced sperm quality.
Deficiency, risk groups, and pregnancy
B12 deficiency is more common in people who eat little or no animal products, in certain gastrointestinal conditions, and with increasing age. During pregnancy, B12 levels normally decrease, and deficiency is therefore somewhat more common in pregnant women. Symptoms of deficiency can include fatigue, tingling in the hands and feet, and cognitive sluggishness. The Swedish Food Agency recommends vegans – and vegetarians who eat very few eggs and dairy products – to take B12 supplements. If you suspect a deficiency, you should get tested through healthcare rather than guessing.
Do you need supplements?
For those who eat a mixed diet with meat, fish, eggs, or dairy products, B12 needs are usually met by food. Supplements are particularly relevant for vegan or heavily plant-based diets, and may be considered in consultation with healthcare if a deficiency is confirmed or risk factors are present. A supplement does not replace an investigation – if you have been trying to conceive for a long time, it is worth seeking medical care for a comprehensive assessment.
Frequently asked questions
Can B12 supplements help me get pregnant?
There is no strong evidence that B12 supplements increase the chance of getting pregnant in people without a deficiency. Good B12 status is part of overall nutritional status, but supplements are primarily justified in cases of low or insufficient intake, for example, with a vegan diet.
How do I get enough B12?
B12 is primarily found in animal products such as meat, fish, seafood, eggs, and dairy products. If you eat plant-based, fortified products and supplements may be needed to meet your needs.
How do I know if I have a deficiency?
Deficiency is detected through a blood test via healthcare, sometimes supplemented with markers such as homocysteine and methylmalonic acid. Do not guess based on symptoms – let healthcare assess it.
This text is general information and not medical advice. It does not replace an individual assessment. Consult your healthcare provider if you have questions about your fertility, suspect a nutritional deficiency, or are considering dietary supplements, especially if you are pregnant or breastfeeding.