Not everyone has the same risk of a B12 deficiency. The following groups receive less B12 or absorb it less effectively due to their diet, age, or medication use:

Vegans and Strict Vegetarians 

Vitamin B12 is naturally found almost exclusively in animal products. Those who eat a completely plant-based diet will hardly get any B12 without supplementation or fortified foods. For vegans, a B12 supplement is almost always necessary to maintain adequate levels.

Elderly (60+) 

As you age, the production of stomach acid and intrinsic factor decreases—two substances needed to absorb B12 from food. In people over 60, active absorption often declines significantly, even with sufficient intake through food.

Users of Antacids 

Antacids (PPIs like omeprazole or pantoprazole, and H2 blockers) reduce stomach acid production. Since stomach acid is needed to release B12 from food, prolonged use can lead to a gradual deficiency. This also applies to long-term use of metformin (a commonly used diabetes medication).

People with Digestive Disorders 

In conditions such as celiac disease, Crohn's disease, atrophic gastritis, or after gastric bypass surgery, B12 absorption may be reduced, even with sufficient intake.

What can you do about a B12 deficiency? 

A B12 deficiency can usually be corrected effectively—but the approach depends on the severity and the cause. For mild deficiencies, a daily supplement is often sufficient; for more severe deficiencies or absorption problems, your doctor may suggest a higher dosage or injections.

Step 1 — Have your B12 status measured 

Before you start supplementing, it's wise to have your status checked. Ask your GP for a blood test that measures both total B12 and active B12 (holotranscobalamin) and homocysteine. This provides a more complete picture than just the total B12 number, which can sometimes appear normal while there is still a functional deficiency.

Step 2 — Adjust your diet 

For those who do eat animal products, B12 is found in liver, fish (especially salmon and tuna), eggs, and dairy. For vegans, only fortified products (some plant-based milks, nutritional yeast, and breakfast cereals) are a reliable source—but for most vegans, this alone is not enough, and supplementation remains necessary.

Step 3 — Choose a supplement 

When supplementing, there are two main forms to choose from: synthetic cyanocobalamin and the biologically active forms methylcobalamin and adenosylcobalamin. The synthetic form must first be converted by the body into the active form before it can be used—the active forms can be used directly, without that intermediate step.

For people with reduced absorption (due to age, antacids, or metformin), a high-dose supplement has the advantage that, in addition to active absorption via intrinsic factor, a small part is also absorbed via passive diffusion—about 1% of the dosage is absorbed in this way, regardless of the status of intrinsic factor. Therefore, a daily dose of 500 to 2000 µg is often a sensible choice for these groups.

There are three common forms of B12 on the market. Here's a brief overview of the differences:

Cyanocobalamin 

The synthetic form found in many inexpensive supplements. Stable and cheap to produce, but the body must first convert it into the active forms before it can be used. This conversion releases a (very small) amount of cyanide — harmless in normal dosages, but for some people, a reason to choose the natural forms.

Methylcobalamin 

One of the two biologically active forms. Works directly in the blood plasma, cytoplasm, and cerebrospinal fluid. Important in homocysteine metabolism and in the production of neurotransmitters.

Adenosylcobalamin (also known as dibencozide) 

The other biologically active form. Works in the mitochondria of tissues and is involved in the citric acid cycle — the link where food is converted into cellular energy.

A supplement that combines both active forms (methyl- and adenosylcobalamin) covers both areas of action simultaneously, without the body having to make a conversion step.

A B12 deficiency is easy to recognize, easy to measure, and — in most cases — easy to supplement with the correct form and dosage. For those who belong to a risk group (vegans, elderly, users of antacids or metformin), periodic attention to B12 status is simply part of conscious health management. If in doubt: have your status measured and discuss with your doctor or orthomolecular therapist which approach suits you.

Want to read more about Energy & Fatigue? View our Energy & Fatigue collectionon Plenthera, which includes magnesium, iron, B-complex, and Q10.

Disclaimer: This article is informative in nature and does not replace medical advice. A dietary supplement is not a substitute for a varied and balanced diet and a healthy lifestyle. If in doubt or taking medication: consult a doctor or pharmacist. Do not exceed the recommended daily dosage. Keep out of reach of young children.