Why “Normal” Vitamin B12 Levels Could be Fooling You — And What to Do About it

Every person on this planet should read and truly digest this — because what you don’t know about your Vitamin B12 status might be silently harming your brain, energy levels, and long-term health.

Many of us have read about Vitamin B12 deficiency and how it can cause a whole host of problems including the nervous system, brain function, energy production, red blood cell formation, and DNA repair.

I’m going to cut right to the chase and then give you the details:

A “NORMAL” Vitamin B12 Blood test does not mean your cells are actually getting adequate Vitamin B12 — In fact they may be starving. Why?

Why a Standard Vitamin B12 may give you False Assurance

A standard Vitamin B12 tests the total Vitamin B12 in your blood, however, it does not distinguish between the active and inactive form — The active form is the form your body actually uses at the cellular level.

Here’s a simple analogy

It’s like being in a desert and having a large jug of water, but not being able to open the cap. The water is plentiful, but you cannot use it. So, someone calls you in the desert and asks “Do you have water”? You respond, sure! I just can’t open the damn bottle! It’s useless.

And that’s what happens when genetic mutations impair methylation, hindering the activation of Vitamin B12 and folate for cellular use.

So, people may have what appear to be normal levels of Vitamin B12 on their blood test, but these mutations reduce the body’s ability to convert folate and Vitamin B12 into their active forms, leaving cells starved despite normal blood levels. So on paper, they’re not technically deficient, but they are functionally deficient.

Why do some people have normal levels of Vitamin B12 levels in their blood but their cells cannot access it?

The MTHFR or MTR/MTRR Mutation is the culprit

It’s all about the genetics you inherited from your mother and father. A few things to know about these genes

1. There’s more than just one specific gene
2. You inherit one copy of each gene from each parent
3. If you have one mutation — which means you got it from one parent but not the other — your ability to process B12 may be slightly reduced — This is known as heterozygous. If you have two mutations — which means you got it from both parents — your ability to methylate could be severely impaired — this affects about 10% of the nation.
4. Being heterozygous for multiple variations of the MTHFR gene is also not optimal and can severely diminish your body’s ability to process Vitamin B12.

How do you Know if Your Body is Actually Using Vitamin B12 Properly?

1. Methylmalonic Acid (MMA) Test — Very specific to B12 deficiency. If B12 is low, MMA rises because it can’t be converted into succinyl-CoA. If this level is high, it shows you’re not effectively converting B12 into its active form. This test detects early actual cellular level B12 deficiency.
2. Homocysteine Test — This is an inflammation marker that builds up when the body can’t methylate properly due to low active B12 and low folate. It’s a better functional indicator than B12 alone.
3. Holotranscobalamin (holoTC) Test — This measures the form of B12 that’s actually bioavailable and can be taken up by your cells. Many practitioners worldwide say this test is the gold standard because it is the most accurate early indicator of B12 status — The problem? It’s not routinely offered by major U.S. labs like Quest Diagnostics or LabCorp, often requiring specialized testing.
4. MTHFR or MTR Genetic Mutations Test — This test will tell you if you have one or more of the genes that predispose you to this B12 methylation issue.

Experts agree that the combination of these tests will give a much clearer picture of how your body is processing Vitamin B12 and how much is available to your cells.

This Isn’t Just About Vitamin Absorption — It Affects Your Whole Body

If you have any of the MTHFR gene mutations that affect methylation, it could affect:

1. Processing toxins
2. Breaking down excess hormones (like estrogen)
3. Neutralizing histamine
4. Creating glutathione (the main antioxidant in your body)
5. DNA Repair
6. Neurotransmitter balance (dopamine, serotonin, norepinephrine)

If methylation slows down because you have one of the mutations (30–40% of the country has it, but effects can vary from person to person)

1. Toxins build up — Toxins like mercury may accumulate more easily, so some experts suggest limiting high-mercury fish as a precaution
2. Glutathione drops — Your liver becomes less effective at detox
3. Homocysteine rises — Increases inflammation and adds to cardiac risk
4. Estrogen clearance may slow, potentially contributing to hormonal imbalances
5. Mental health issues may surface — Anxiety, depression, brain fog, etc

What You Can Do If You Have These Genetic Mutations

1. Consult with an Integrative or Functional Medicine Doctor — Don’t go at this alone

They may suggest some of the following:

1. Choose an active-B complex vitamin
2. Consider Glutathione and its precursors like NAC (N-Acetyl Cysteine)
3. Alpha lipoic acid
4. Sulfur-rich foods
5. Liposomal glutathione or S-Acetyl glutathione

Most importantly, consult with an MTHFR-literate doctor such as a Functional or Integrative Medicine doctor. They don’t just look at your lab values and call it a day — they look at how your body is functioning, especially at the genetic and cellular levels. They will also know precisely which tests to order and which supplements you should be taking based on the results of your tests and your symptoms (if any).

The older you get, the more these issues can affect you as your detoxification and methylation pathways become more critical.

You can use this tool to find a functional medicine doctor:
https://www.ifm.org/find-a-practitioner

Be well. Be informed. And remember — when it comes to your health, sometimes the truth is hiding in plain sight.

https://medium.com/health-science/the-hidden-epidemic-right-under-our-noses-13b823df26c8