Vitamin B12 deficiency: signals, who is more likely to have one and how much per day

A vitamin B12 deficiency creeps up on you. Your body has a reserve that lasts months to a year, so you only notice something once it has run out. And the first complaints, tiredness and dizziness, point to a hundred other things. Below you can read which signals tell you it is a B12 deficiency, who is more likely to have one, what a blood test does and does not say, how much B12 you need per day and how you top up.

Symptoms of a vitamin B12 deficiency

Vitamin B12 is needed to make red blood cells and for the proper working of the nervous system. A deficiency therefore shows in two ways, as the Netherlands Nutrition Centre describes it:

• Anaemia (macrocytic anaemia): tiredness, dizziness, palpitations and ringing in the ears.
• Neurological complaints: tingling in the fingers, memory loss, coordination problems and muscle weakness in the legs.

The neurological complaints are the reason to take a deficiency seriously. They can develop without anaemia, and if you wait long they do not always recover fully. If you recognise tingling, numbness or unsteady feet alongside the tiredness, see your GP.

Who is more likely to have a B12 deficiency?

B12 is found almost only in animal products. It is made by bacteria in the digestive tract of animals and so ends up in meat, fish, eggs and dairy. Humans make it too, in the large intestine, but do not absorb it there. Two routes to a deficiency:

• Taking in too little. Anyone who eats no animal products gets no B12 from ordinary food. For vegans a supplement or fortified food is therefore not a choice but a necessity. Vegetarians who eat little dairy and egg are at risk too.
• Poor absorption. To absorb B12 from food you need stomach acid and a protein from the stomach lining. In older people stomach acid decreases, and long-term use of acid-suppressing medication or the diabetes drug metformin can lower absorption. The same applies after stomach surgery or with bowel disease. In pernicious anaemia the body no longer makes that protein itself; then food does not help and your GP is the only route.

What does a B12 value say?

Your GP measures vitamin B12 in the blood. A clearly low value confirms a deficiency. A value in the grey area says less: your GP can then have methylmalonic acid or active B12 determined as well, because those respond earlier to a deficiency in the cells. The thresholds differ per laboratory, so do not compare your result with a number from the internet but discuss it with your GP. If you already take a supplement, say so: it affects the result.

How much vitamin B12 per day?

The recommended daily amount is 2.8 micrograms for adults, 3.3 micrograms for pregnant women and 3.8 micrograms when breastfeeding. For children the adequate intake rises from 1.0 microgram (age 1 to 3) to 2.6 micrograms (age 15 to 17). For comparison: a 100 gram piece of salmon provides 4 micrograms, 75 grams of beef 1.6, an egg 0.8 and a glass of semi-skimmed milk 0.7 micrograms.

Supplements contain far more than those 2.8 micrograms, often 10 to 1,000 micrograms. That is not a mistake. Of a large dose only a small part is absorbed through a second route that needs no stomach acid, and it is exactly that route that still works when absorption from food falters. An excess is no concern: there is no tolerable upper level for B12, and no adverse effects are known in people who took a lot for a long time. The body limits absorption itself.

Topping up a B12 deficiency

Once a deficiency is proven, your GP decides the approach: high-dose tablets or injections, depending on the cause. With an absorption problem injections are sometimes the only option. The blood value recovers within weeks to months; neurological complaints need longer. Do not stop on your own when you feel better, because with an absorption problem the deficiency comes back.

If there is no deficiency but you want to prevent one, for instance because you eat plant-based, a daily supplement is enough. Vitamin B12 contributes to the reduction of tiredness and fatigue, to normal energy-yielding metabolism, to normal functioning of the nervous system and to normal red blood cell formation.

When do you take B12?

The moment does not matter and a meal is not needed; B12 is water-soluble. Many people take it in the morning, together with other B vitamins. It can be taken with almost anything, including iron, magnesium and vitamin D. Which combinations you do keep apart is in which vitamins can you take together.

Which supplement fits?

The vitamin B12 capsules by Together contain 20 micrograms of B12 per capsule, 800 per cent of the reference intake, in three natural forms: methylcobalamin, adenosylcobalamin and hydroxocobalamin, extracted from shiitake and oyster mushroom. One a day, vegan, in a plant-based capsule.

If you want the whole B group in one go, the B complex by Together contains 10 micrograms of B12 as methylcobalamin, alongside 400 micrograms of folic acid and the other B vitamins. Folate and B12 work together in the body in making blood. If you eat fully plant-based, also have a look at the vegan multi by Together, which besides B12 also contains iron, iodine and vitamin D: the nutrients a plant-based diet more often falls short on.

A supplement does not replace a diagnosis. If you recognise the complaints above, have it measured.

Frequently asked questions about a B12 deficiency