Transcription
There is a deficiency affecting a significant proportion of people around the world that can damage your nervous system. It can accelerate cognitive decline. It can mimic depression and also be mistaken for early dementia. And the standard blood test used to detect this, it will miss it in a meaningful number of people. That is what the peer-reviewed literature actually tells us. And yes, I'm talking about vitamin B12 here.
Now, the really frustrating part about all of this is that the test itself is fundamentally flawed. It measures total B12 in your blood, but a significant portion of that circulating B12 is actually bound to proteins that don't actually deliver it to your cells. So, it shows up on the blood test. It counts towards the number, but it does almost nothing useful at all. Which means that somebody can go to their doctor with exactly these symptoms. They can get a blood test. They can get told that everything is absolutely fine and then go home reassured. Not because their doctor is incompetent, but because the test they're relying on is not fit for purpose.
If you're new here, then hello, welcome to the channel. I'm Dr. Alex. I'm an emergency medicine doctor and I've seen this play out in real patients who have been admitted for falls and confusion for weakness where the root cause turned out to be a B12 deficiency that had been sitting there for years missed on every single blood test because the number was technically within range and that shouldn't happen but it does routinely and regularly and understanding why is most of the battle. So, in this video, I'm going to talk you through 11 signs that your B12 could be too low, including several that almost never appear on these lists. I'm going to explain what B12 actually does in your body at the cellular level, why absorption failure is the real story here rather than just diet, and crucially, what tests you should actually be asking for instead.
So, vitamin B12 is what we call a co-actor. That means it's not doing one job inside your body. It's sitting at the center of several critical reactions that can't run without it. The two that matter most for understanding deficiency are myelin synthesis and DNA replication in your bone marrow. So myelin is the protective sheath around your nerve fibers. Every single nerve in your body. So your peripheral nerves in your hands and feet, the pathways in your spinal cord, the white matter in your brain, every single one of them is wrapped in this protective myelin. It's what allows electrical signals to travel really fast and accurately. And without it, signals slow down. They start distorting and eventually they start to fail. So B12 is essential for maintaining that protective sheath. When B12 levels drop, myelin starts to break down and that degradation is the origin of almost all the neurological symptoms on this list.
Now, the part about bone marrow is actually about red blood cell production. So, B12 works alongside folate to allow proper DNA replication inside developing blood cells. When B12 is insufficient, those cells can't divide normally. They become what we call megaloblastic, abnormally large and fragile and deeply ineffective at carrying oxygen. So the result is a specific type of anemia that produces fatigue and breathlessness and pallor as well. Not from blood loss or bleeding but from blood that fundamentally can't do its job properly.
Now there is a third piece here that doesn't really get enough attention and that is homocysteine. So B12 is required to convert homocysteine, which is a metabolic byproduct, into methionine. When B12 falls, homocysteine accumulates and elevated homocysteine is independently toxic to blood vessels and your brain tissue and it's associated with accelerated cognitive decline and cardiovascular disease. So deficiency here isn't just about nerves and blood. It is also a long-term vascular risk as well.
Now, here's the part that surprises a lot of people. Your liver stores vitamin B12, and those stores can last around 2 to 5 years, which means that somebody can develop an absorption problem today and feel completely normal for 2 or 3 years while their stores very slowly drain away. So by the time symptoms appear, the deficiency has typically been present for a long, long time and the neurological damage in many cases is already underway before the blood count changes at all and that is from a substantial body of work including studies published in the New England Journal of Medicine. Basically, this idea of neurological compromise preceding any changes to your blood is well, well established.
And then talking about absorption here for a moment. So a lot of people seem to assume that a B12 deficiency is a vegan problem, but it's not. The majority of serious B12 deficiencies in adults over 50 happens in people who actually eat meat and fish and eggs. They are consuming good amounts of B12, but their gut simply can't absorb it. This whole process requires adequate stomach acid to release B12 from food proteins, and then a very specialized protein called intrinsic factor to carry it to the terminal ileum where it's actually absorbed. Now, if either of those steps fails through age-related decline in stomach acid or long-term use of proton pump inhibitors or autoimmune damage to the cells that produce intrinsic factor, the absorption pathway breaks down entirely. So you could eat liver or meats every single day that is really high in B12 and still become profoundly deficient.
So let's talk about the 11 signs then. So the first one is fatigue. This is one that's almost universal in B12 deficiency and almost universally misattributed as well. So the fatigue that we're talking about here isn't sleepiness. It is like a systemic heaviness, a physical and cognitive and emotional fatigue all at once. And it's one that a good night's sleep doesn't touch because the problem isn't overexertion. It is your blood physically being unable to carry enough oxygen to your tissues. Patients often describe it as wading through mud or functioning at 60% of normal. The ceiling on their energy has quietly dropped over months and they've adjusted to it so gradually that they don't realize how significant the change is.
The second sign is tingling or numbness in the hands and feet. Now, this one is the most diagnostically specific early neurological symptom and it's the one that I want people to take really seriously. So when myelin breaks down in the peripheral nerves, specifically the long sensory nerves running into the extremities, the signals can become quite disrupted. The sensation here is typically described as pins and needles or feeling a bit numb or sometimes like a buzzing or a faint electric feeling. It tends to be quite symmetrical, so both hands or both feet. And then it's often worse at night as well. Now research published in the journal of neurology has confirmed that this peripheral neuropathy is frequently misattributed to diabetes or poor circulation, which delays correct diagnosis by months or even years. And critically, if the deficiency is left untreated beyond somewhere between sort of 6 months and a year with these neurological symptoms, that nerve damage can become permanent. It's not just uncomfortable, it is a countdown to something more serious.
Sign number three is unexplained muscle weakness. So when tissues are chronically under-oxygenated, skeletal muscle, the muscle that you can see, is one of the first to feel it. And what this means is your muscles fatigue faster. They recover more slowly and they lose strength over time. But there is also a very direct neurological component. So when the motor pathways in the peripheral nervous system begin to demyelinate, the signal from the brain to the muscle becomes impaired. And people notice this as a general weakness, as a difficulty with tasks that require sustained grip or effort, legs that feel heavier than they should. In older people, this contributes directly to falls and loss of independence. So this is really, really important as you get older and from my experience, a lot of doctors put this down to just age-related muscle loss or sarcopenia before checking their B12.
Okay. Sign number four is balance problems, particularly at night. Now this is a more advanced symptom and it signals that the deficiency has progressed to affect the spinal cord itself. Now there's a specific condition called subacute combined degeneration of the spinal cord caused by a B12 deficiency that damages what we call the dorsal columns and these carry proprioceptive information. Now proprioception is your body's sense of where it is in space and when those pathways degrade, you lose unconscious feedback from your feet and your legs and so balance becomes quite difficult. It becomes effortful. So, in a well-lit room, your vision can compensate quite well. But in the dark or on an uneven surface, this deficit becomes quite obvious. People notice that they start feeling significantly less stable at night or that they instinctively look at their feet when they walk. So, in the context of B12 deficiency, this isn't clumsiness. This is a spinal cord demyelination and it needs to be investigated urgently.
The fifth sign is actually mood changes. So things like depression or feeling really emotionally flat. And the reason this is important is that B12 is essential for making things like serotonin and dopamine, which are the brain's main mood chemicals. So when B12 drops, the brain simply can't produce enough of them. And what this looks like isn't always textbook depression. Most of it is a flatness, an irritability, or a quiet withdrawal from things that used to matter to people. So, people don't usually say, "I'm depressed," or really anxious. They just say they don't feel like themselves anymore. The critical problem is that antidepressants will not fix a mood problem caused by a missing vitamin. And research in the journal of psychopharmacology has actually shown that people with low B12 respond significantly worse to antidepressant medications. So giving these people pills is the wrong thing to do when they have a B12 deficiency. But what happens is that the drugs get adjusted, the doses go up, and the real cause goes uninvestigated, sometimes for years.
Now, sign number six is cognitive changes. And this is things like brain fog or memory lapses or word-finding difficulty. This is the one that causes the most damage when it's missed because it looks almost identical to early dementia. So, slow thinking or forgetting words mid-sentence or short-term memory that feels unreliable, these come from two things happening at once. The nerve pathways in the brain are losing their protective coating. So signals start slowing down and also a toxic compound called homocysteine, which I've already mentioned, which B12 normally clears from the body, starts to build up and directly damage the brain tissue. Research in the journal neurology has actually linked elevated homocysteine to faster brain shrinkage and significantly higher dementia risk. Now, to be clear, B12 deficiency doesn't cause true dementia in a way that Alzheimer's does. What it causes is a set of cognitive symptoms that can look and actually feel identical to early dementia, but which are driven by a correctable deficiency rather than irreversible neurodegeneration, if that makes sense. The danger here is that many people with this presentation receive a dementia diagnosis. They get told nothing can be done for it and they never have their B12 properly investigated. If B12 is the underlying driver, then treating it can actually reverse much of what's happening and that is a completely different prognosis and it is being completely missed in a huge number of people.
The seventh sign is a smooth or painful or inflamed tongue. Now, this is one that you can actually check yourself right now in the mirror. So normally the tongue has a slightly rough or textured or sort of sandpapery surface from tiny projections called papillae. Now when B12 is low, those projections can break down because the cells that maintain them can't replicate properly. The tongue then becomes smooth and shiny and often red and painful. So, eating becomes uncomfortable, your taste can change, and some people get a persistent burning sensation that the dentist or GP hasn't been able to explain. It usually appears alongside mouth ulcers as well. It's a really easy sign to overlook, but it's a direct physical signal that something is wrong at the cellular level.
Okay, moving on to number eight. We've got pale or slightly yellowed skin. Now people will assume that these sort of seem like opposites, but they happen together. So the paleness comes from anemia, which is fewer working red blood cells means the skin loses its normal color. The yellow comes from something very different. So abnormal red blood cells produced during B12 deficiency are fragile and they get broken down by your spleen over here faster than normal. Now that breakdown releases a substance called bilirubin, which gives the skin and the whites of your eyes a faint yellow cast. Now it's nothing like the dramatic jaundice of liver failure, it's very subtle, but alongside fatigue and pallor, it's a combination that should make people think of a B12 deficiency.
Moving on to number nine, we've got heart palpitations or breathlessness on minimal exertion. So when the blood can't carry enough oxygen around the body, the heart works harder to compensate. It beats faster and with more effort just to keep up. And what that produces is a racing or pounding feeling even at rest. So during any physical effort, the demand for oxygen outstrips what the blood can deliver and then breathlessness follows. So getting up quickly or climbing the stairs or walking to the car, none of these should leave somebody struggling for breath. But when they do and a cardiac assessment comes back normal, anemia from a B12 deficiency is a diagnosis actively worth pursuing.
The 10th sign is visual disturbances. Now, a B12 deficiency can affect the optic nerve, the nerve that carries visual information from the eye to the brain, in the same way that it affects the nerves elsewhere in the body, which we've already talked about. The protective coating breaks down, the signals become distorted, and vision starts to change. It typically shows up here as a gradual blurring or dimming of central vision or colors appearing less vivid than they used to. And again, it's really easy to put this down to something like needing new glasses or screen fatigue or just getting older. But in somebody who already has other signs of B12 deficiency, this needs investigating promptly because optic nerve damage, if left long enough, can become permanent.
And then finally, the 11th sign on this list is disrupted sleep. That makes no sense. So B12 is involved in producing melatonin, which is the hormone that controls when you feel sleepy and when you wake up. And research, including work from Japan, specifically looking at B12 and the body clock, suggests that deficiency can actually disrupt sleep in ways that go beyond just feeling tired. So people describe lying awake despite feeling exhausted or waking up too early or sleeping for a full night and feeling like they barely rested. And that feeds directly back into the fatigue, the mood, the cognitive fog that we've talked about. It becomes a cycle that's almost impossible to break without addressing what's actually driving it.
So if you recognize several of these symptoms in yourself, the biggest barrier here to getting answers is the test that is supposed to actually provide those answers. Most labs only flag a problem below 150 to 200 picograms per liter. But the research tells us that nerve damage can occur at levels well above that. A study in the American Journal of Clinical Nutrition found that up to 40% of people in the low normal range have a real deficiency at the cellular level. Their tissues aren't getting enough B12 even though the numbers look acceptable on paper. Someone sitting at 240 or 260 get told they're fine and then sent home while the damage continues. The two tests that actually catch this are methylmalonic acid and homocysteine. Both of them rise when the body is genuinely short of functional B12, regardless of what the standard test shows. Neither of them are run automatically. You have to ask for them by name or very often pay for them. If your B12 is below 300 picograms per liter and you have any of these symptoms, then that is a conversation worth having with your doctor, even if your result is technically within the normal range.
So the highest risk group here is adults over the age of 50 because stomach acid naturally declines with age and B12 absorption actually depends on that. So anybody on long-term omeprazole or lansoprazole or pantoprazole or esomeprazole, and I did a video on these medications a couple of weeks ago, these are common acid-suppressing medications. These people face the same problem for the same reason. Now, another one is metformin, one of the most widely prescribed diabetes medications. We know that this interferes with B12 absorption in the gut. There is NHS guidance recommending B12 monitoring in long-term users, but to be honest, it's not consistently followed. Anybody who's had stomach surgery as well, or anybody who has an autoimmune condition affecting the stomach lining, these are also at significant risk as well.
So after all of that, if you're concerned by anything in this video, then you need to ask your doctor specifically for three things: a serum B12 blood test, methylmalonic acid, and also a homocysteine. All of those are blood tests, not just the standard blood panel. Because as we've covered, that alone isn't enough. If a deficiency is confirmed, then what happens next depends on why it's happening. In most people over the age of 50, the problem isn't that they're not getting enough B12, it's that their gut has lost the ability to absorb it properly. In that situation, taking a B12 tablet every day often won't work because the tablet relies on the same broken down system to get into the body. An injection delivers B12 directly into the bloodstream and gets around that problem entirely. So, your GP can arrange this for you.
For people on a plant-based diet where the issue is simply not consuming enough B12 in the first place, a high-dose daily supplement around 1,000 micrograms can work because a tiny amount of B12 can actually sneak through into the bloodstream through a back door that doesn't need the gut to be working properly, if that makes sense. If the deficiency is caused by a condition called pernicious anemia, where the body attacks the cells responsible for B12 absorption, injections will be needed for life. And if it's linked to diabetes medication called metformin, which is a very common cause that gets overlooked, like we've talked about, then supplementation and a conversation about the medication itself should both happen at the same time.
And just to close on this, a B12 deficiency is one of the most treatable conditions in medicine. If you catch it early enough, then the recovery is remarkable. Your fatigue can absolutely lift, your mood can stabilize, your cognitive fog can absolutely clear, and your nerve symptoms can resolve. The nervous system can absolutely heal when it gets what it needs. But the window here is really important. Every month of undetected deficiency is another month of damage accumulating. And again, the problem with all of this is that the test that is meant to catch this often doesn't. But that shouldn't be a reason for you to panic. It is a reason to know the signs and symptoms, to ask for the right tests, and not simply accept a normal blood test result as the final answer if something still doesn't feel right.