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Could your vit B12 level be normal on a blood test and still not tell the whole story?
In this video, we take a closer look at vit B12, what a normal vitamin B12 result really means, and why the laboratory reference range may not always reflect what is happening inside your cells.
Vitamin B12 plays a critical role in the nervous system, blood cell production, and important metabolic reactions throughout the body. But vit B12 deficiency can develop gradually, and symptoms may appear before the diagnosis becomes obvious.
You’ll learn:
• Why vit B12 reference ranges can differ between laboratories
• Why a normal serum vit B12 level does not always exclude deficiency
• How vitamin B12 affects methylmalonic acid, or MMA, and homocysteine
• Why MMA may provide additional information when a vit B12 result is borderline
• What a borderline vitamin B12 level may mean
• Why symptoms and risk factors should be considered alongside the laboratory result
• When further testing for vit B12 deficiency may be appropriate
If your vit B12 result falls within the normal range but you still have symptoms or risk factors for vitamin B12 deficiency, the number on the report may deserve a closer look.
The important message is simple: normal is not always normal on a vit B12 report.

References:

Tillemans MPH, Giezen TJ, Egberts TCG, Kalisvaart KJ.
The association between medication use and vitamin B12 deficiency in the elderly population: a cross-sectional study. BMC Geriatrics. 2026;26:294.
https://doi.org/10.1186/s12877-026-07040-6

Chatthanawaree W.
Biomarkers of cobalamin (vitamin B12) deficiency and its application. Journal of Nutrition, Health & Aging. 2011;15(3):227–231.
https://pubmed.ncbi.nlm.nih.gov/21369672/
https://doi.org/10.1007/s12603-010-0280-x

Ueno A, Hamano T, Enomoto S, et al.
Influences of Vitamin B12 Supplementation on Cognition and Homocysteine in Patients with Vitamin B12 Deficiency and Cognitive Impairment. Nutrients. 2022;14(7):1494.
https://pmc.ncbi.nlm.nih.gov/articles/PMC9002374/
https://doi.org/10.3390/nu14071494

This video is for educational purposes and is not a substitute for individual medical advice. Discuss abnormal or unexplained symptoms and laboratory results with your healthcare professional.

#VitB12 #VitaminB12 #B12Deficiency #VitaminB12Deficiency #B12BloodTest #MMA #Homocysteine #BloodTests #LabResults
Transcript
00:00Are you tired all the time?
00:02Do you find yourself being a little forgetful sometimes?
00:06So you decide to check it out with your doctor,
00:09just to be certain everything is okay.
00:12And everything is A-OK, including your vitamin B12.
00:18But wait a minute.
00:20Could you still be vitamin B12 deficient?
00:24Your doctor told you your B12 level was normal.
00:28He showed you the report.
00:30You could see for yourself that it is normal.
00:33So what could be the disconnect here?
00:36Pay close attention and I'll walk you through a scenario
00:39that clinicians encounter across the country
00:41in medical facilities and clinics.
00:44Vitamin B12, you see, is a co-factor.
00:49Your level stores a remarkable amount of vitamin B12,
00:53often enough to keep you going for several years.
00:57That is why vitamin B12 deficiency doesn't just happen overnight.
01:04You don't just wake up one morning and say,
01:07oh, my memory isn't like it used to be.
01:10I must be vitamin B12 deficient.
01:13And that's what makes it tricky.
01:16B12 deficiency can develop gradually.
01:20And the symptoms, the serum B12 concentration,
01:24and changes in the blood count do not necessarily appear at the same time.
01:31During this critical period, if deficiency is developing,
01:36your memory, blood cells, and nervous system can gradually begin to suffer.
01:42And here's the worst part.
01:45Neurologic damage from B12 deficiency can often improve when it's caught early.
01:51But if severe deficiency goes untreated for too long,
01:56that damage may become permanent.
01:59Here's something even stranger.
02:02Researchers took samples from 300 healthy people
02:06and measured the B12 using three commonly used laboratory systems.
02:12And here's what they found.
02:13With Roche, the normal range was from 190 to 678,
02:18picograms per milliliter.
02:20With Siemens, it was 181 to 562.
02:24With Beckman, it was 110 to 562.
02:29Same vitamin, same group of people,
02:33different laboratory methods,
02:35different reference ranges.
02:37So what counts as a normal B12
02:39can depend on what machine your laboratory uses.
02:44But that's only half of the story.
02:47There's another reason that B12 numbers can sometimes fool you.
02:52Vitamin B12 helps the body convert homocysteine to methionine.
02:57It also helps the body convert methylmalonic coenzyme A
03:02to succinylcholinezyme A.
03:04When B12 is deficient,
03:07both of these reactions can become impaired.
03:10And when those B12-deficient reactions slow down,
03:16methylmalonic acid and homocysteine can begin to rise.
03:20But that gives us something very useful.
03:25It gives us biochemical clues that B12 isn't doing its job properly.
03:31And here's the part most people don't realize.
03:35The vitamin B12 level we measure in the blood does not always perfectly reflect the vitamin B12 levels in the
03:42tissues.
03:43The B12 on your laboratory report is total B12 circulating in the blood.
03:50It is not a direct measurement of how much usable B12 is actually inside your cells.
03:58So your lab report can show a normal serum vitamin B12 level and your tissues can be telling a completely
04:06different story.
04:07What's the solution?
04:10How do you protect yourself from the devastating effects of vitamin B12 deficiency?
04:15If you have any of the symptoms of B12 deficiency and your B12 level is somewhere in that borderline zone,
04:24roughly 180 to 350,
04:27150, don't just look at the word normal printed beside it.
04:32That may be a situation where your doctor needs to consider another marker,
04:39particularly methylmalonic acid, MMA, and sometimes homocysteine.
04:45As I mentioned before, these can rise when your tissue vitamin B12 is low.
04:51And sometimes those markers can be high even when your serum B12 is borderline or occasionally still within the normal
05:01range.
05:02Remember, normal is not always normal on a vitamin B12 report.
05:08I hope you found this video useful.
05:10If you did, like and share the video with your friends and family.
05:14You can support this channel by subscribing.
05:16Until the next video, stay healthy and stay safe.
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