Normal Vitamin B12 Levels: Both Unit Scales, and by Age

1. Does the normal B12 range change with age?

No. This is the honest answer, and it is more useful than any chart. UK labs report one cut-off at every age. A 25-year-old and an 80-year-old are measured against the same line.

Folate is read beside B12 almost every time, so it is worth checking folate levels by agein the same sitting.

Most UK labs flag total serum B12 below 148 pmol/L as deficient. Results between 148 and 258 pmol/L sit in an indeterminate band. That band is where most of the arguments happen, and it is the same band at every age.

Check which unit your report uses before you compare anything. UK labs use either pmol/L or ng/L, and the numbers look nothing alike. To convert, multiply ng/L by 0.738 to get pmol/L, or use our B12 unit converter.

So the 148 pmol/L cut-off above is the same line as 200 ng/L, and a result of 320 ng/L is about 236 pmol/L. US reports write ng/L as pg/mL. Those two are the same thing.

So the age charts you find elsewhere are not reference ranges. They are averages, and an average tells you what is common rather than what is healthy for you. Our guide to reference ranges explains why that distinction matters on every marker, not just this one.

2. How common is low B12 after 60?

Common enough to change how you read a borderline number. A review in the American Journal of Clinical Nutrition pooled large surveys from the UK and the United States. It found that around 6% of people aged 60 and over were deficient, on a cut-off of 148 pmol/L.

The marginal group is bigger. Closer to 20% of older adults sat between 148 and 221 pmol/L. That is inside the printed range, and it is exactly where a result like 210 lands.

3. Why does B12 get harder to absorb as you age?

Because the problem moves. In younger adults, low B12 is usually about intake. B12 comes from animal foods, so vegans and vegetarians carry the risk. Our vegan blood test guide covers that side.

In older adults the cause shifts to absorption. The same AJCN review found that food-bound B12 malabsorption becomes the main cause in later life, driven partly by gastric atrophy. Put plainly: the stomach makes less acid, so it struggles to release B12 from food.

Then there is pernicious anaemia, an autoimmune condition that stops B12 being absorbed at all. The NHS is direct about who it tends to affect.

“The exact cause of pernicious anaemia is unknown, but it’s more common in women around 60 years of age, people with a family history of the condition and those with another autoimmune condition.”

— NHS, Vitamin B12 or folate deficiency anaemia: Causes

That is the age story in one line. Your intake may not have changed at all. What changed is how much of it reaches your blood.

4. Which medicines lower B12 at any age?

This is the part age charts miss entirely. Several common medicines reduce B12 absorption, and they are prescribed at every age. The NICE guideline on B12 deficiency in over-16s (NG239) names them as risk factors.

• Metformin, taken long term for type 2 diabetes.
• Proton pump inhibitors such as omeprazole and lansoprazole. If you have been on one for a year or more, our guide to the blood tests worth checking on long-term omeprazole covers B12 and magnesium together.
• H2-receptor antagonists, the older acid-reducing drugs.
• Nitrous oxide, whether medical or recreational.

Gut surgery matters too. A gastrectomy, a bowel resection or a bariatric operation can all cut absorption. None of this is a reason to stop a prescribed medicine. It is a reason to know your number and to raise it with your GP.

5. What if your B12 is normal but you still feel it?

Take the symptoms seriously and look at the wider picture. Total serum B12 measures everything in your blood, including the portion your cells cannot use. Active B12 measures the usable fraction, so the two can disagree.

NICE also points to the symptoms that matter here: fatigue, cognitive difficulty, glossitis, and tingling or numbness in the hands and feet. Our guide to B12 deficiency symptoms runs through the full NHS list, and which bloods to check for tingling and numbness covers what else can cause it. NG239 says testing is warranted when someone has at least one common symptom and at least one common risk factor.

Two other markers help read a grey-zone result. Folate works alongside B12, and a full blood count shows whether your red cells have grown large, which is a classic fingerprint of low B12. The main B12 blood test guide covers active B12, MMA and homocysteine in full. If a DNA kit has told you about an MTHFR variant, folate and B12 are still the numbers that answer the question.

One caution. Take your sample before that day’s supplement. A B12 tablet can lift the reading without fixing the shortfall behind it.

The same goes for a jab. If you are weighing up a £29 B12 injection from Boots or Superdrug, get the number first, because afterwards the test reads the injection rather than you.

6. Which blood test measures your B12?

Helvy’s Vitamins & Minerals panel (£159) reports B12 alongside folate, vitamin D, magnesium and a full iron workup. That pairing matters, because folate and iron produce a similar kind of tiredness.

If you want a broader first look, the General Energy & Wellness panel (£149) reports B12 with thyroid, cortisol, kidney, liver and cholesterol markers. Both are home finger-prick tests, processed by UKAS-accredited UK labs.

Not sure which fits? The build-my-test tool walks you through it, and the energy and fatigue hub covers the other causes worth ruling out. For the non-medical ones, read what causes low energy levels.

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