Vitamin B12 is the secret energy booster your body craves—but many of us are unknowingly missing out. If you’ve been feeling constantly tired, weak or light-headed or just not yourself, it might be time to look at your Vitamin B12 levels.
While this vital nutrient is found in foods like meat, fish, and dairy, Vitamin B12 deficiency can happen for a variety of reasons: poor absorption, being vegetarian or vegan, having gut issues or an increased need for B12 due to aging. Those with iron deficiency anaemia can often have lower B12 also. Fortunately, it is something you can address easily, and when you do it can make a world of difference to your energy, focus, and overall health.
Why Is Vitamin B12 So Important for Energy and Health?
Think of Vitamin B12 as the spark plug for your body: it’s small but mighty, quietly powering essential functions that keep you feeling your best. Without it, things can start to sputter—low energy, brain fog, or even mood swings might creep in.
It energises your body: B12 helps convert the food you eat into fuel.
Sharpens your mind: Supports focus, memory, and mental clarity.
Keeps your nerves in check: Protects the pathways that carry signals throughout your body.
Promotes healthy blood and heart function: B12 is crucial for red blood cell production and keeping your heart in good shape.
B12 doesn’t work alone, though. It teams up with folate and other B vitamins to keep everything running smoothly.
Where Does B12 Come From?
If you’re a fan of roast chicken, a juicy steak, or a piece of salmon, you’re in luck—Vitamin B12 is naturally found in animal-based foods, making it easy to get your daily dose from:
Meat and poultry: Beef, liver, and chicken are some of the richest sources of B12.
Fish and shellfish: Options like salmon, trout, sardines, and tuna pack a powerful B12 punch.
Dairy and eggs: Foods like milk, yogurt, and cheese offer smaller amounts, but they can still contribute to your intake.
This is something I see all the time with clients: they think their diet should be covering it, yet their B12 levels still come back low. Understanding where B12 comes from—and what might be getting in the way of your body absorbing it—is the first step to making sure you’re getting enough.
What Causes Deficiency?
A Vitamin B12 deficiency isn’t always caused by a lack of B12-rich foods in your diet—sometimes, the real issue is how well your body can absorb and utilise it. Even if you’re eating plenty of B12, certain factors can get in the way:
Gut Health Issues: Problems like low stomach acid, SIBO (small intestinal bacterial overgrowth), or conditions like Crohn’s disease can block Vitamin B12 absorption.
Ageing: As we age, our ability to absorb B12 decreases.
Medications: Long-term use of acid-reducing medications (like PPIs), Metformin or the oral contraceptive pill can lower B12 levels.
Dietary Gaps: Vegans, vegetarians, or those with a nutrient poor diet can miss out. Plant-based foods like fortified cereals and plant milks can help but they’re often not as readily absorbed by the body.
For some, B12 deficiency can sneak up over years, showing up as vague symptoms: tiredness, weakness, memory struggles, or even feeling a bit down. It’s easy to chalk it up to stress or a busy life and it can get overlooked.
How Do You Know If You’re Low in B12?
Vitamin B12 deficiency often goes unnoticed because its symptoms can mimic the effects of a busy lifestyle, stress, or even ageing. But there are certain telltale signs your body might be giving you—subtle at first, but harder to ignore as they build over time. There are some read flags to watch out for:
Constant fatigue or feeling weak.
Brain fog, poor memory, or dizziness.
Tingling in your hands and feet (a sign your nerves are struggling).
Mood changes like low energy, irritability, or feeling down.
A pale or inflamed tongue (a sneaky symptom most people miss)!
For women in their 30s to 50s, hormonal changes like perimenopause can make B12 deficiency even trickier to spot—it’s easy to assume fatigue is just “part of life.”
How to Optimise Your Vitamin B12 Levels
If your B12 levels are low, the good news is that there are effective ways to address it. From identifying the root cause to making targeted changes, you can take steps to boost your energy, sharpen your focus, and support your overall health.
Test First - If you suspect low B12, ask for a blood test. The reference range for Vitamin B12 varies, but sufficiency is often defined as serum levels of 200-900 pg/mL. However, many experts argue that this range reflects only sufficient levels, and that optimal levels above 500 pg/mL are where you really thrive. So don’t settle for being “in range” if your symptoms tell a different story.
Adjust Your Diet
Focus on B12-rich foods like liver, mackerel, sardines, tuna, trout, salmon, beef, dairy, and eggs.
For vegans, look for fortified foods like cereals or plant milks—but note they might not be enough on their own.
Supplement Smartly - If food alone isn’t cutting it, consider:
Methylcobalamin (a natural, active form of B12) or Adenosylcobalamin in sublingual tablets or drops.
B12 injections for more severe deficiencies or absorption issues.
Check Your Gut - If absorption is the issue, working on gut health (like treating SIBO or low stomach acid) can make a huge difference.
If I am working with a client who has low energy levels and they bring their blood results to me one of the areas I look at is their B12 and their folate level. The reference range of 200 to 900 for B12 is so broad and if your levels are 250 for example, you fall within the range and nothing more is thought of it. If this is then coupled with a less than optimum folate level and the client is experiencing fatigue or weakness optimising these nutrients can make a big difference.
Vitamin B12 and Its Role with Other B Vitamins
Vitamin B12 doesn’t work alone—it’s part of a powerful team alongside the other B vitamins including folate (Vitamin B9) and Vitamin B6. Think of them as the ultimate support crew, each playing a unique yet interconnected role in keeping you energised, balanced, and healthy. Together, they help:
Support Energy Metabolism
These B vitamins are like the spark plugs in your body’s energy engine. They work together to convert the food you eat—carbs, fats, and proteins—into usable energy. Without enough B12, B6, and folate, your body can’t efficiently produce this energy, leaving you feeling tired and sluggish, no matter how much you eat or sleep.
Balance Mood and Mental Well-being Feeling irritable, low, or foggy? You might be missing out on this trio of B vitamins. B12, B6, and folate play a key role in neurotransmitter production, helping to create mood-regulating chemicals like serotonin and dopamine. These are the very same neurotransmitters that keep you calm, focused, and in a better mental space. A deficiency in any one of these B vitamins can throw off this delicate balance, potentially contributing to anxiety, low mood, and poor concentration.
Protect Your Heart and Brain Health Elevated levels of homocysteine—a natural amino acid—can damage blood vessels and increase your risk of heart disease, stroke, and even cognitive decline. Here’s where B12, folate, and B6 step in. Together, they convert homocysteine into methionine, a harmless amino acid that your body can use for other processes. This reduces inflammation and supports long-term heart and brain health.
If you’re experiencing low energy, mood swings, or brain fog, the B-vitamin team could be the game-changer you’ve been missing.
My Personal Take
As someone who’s mostly vegetarian but includes fish in my diet, I know how easy it is to fall short on B12 without realising it. To stay on top of my energy and mental clarity, I regularly use a methylated B-Complex supplement. I find it makes a huge difference—helping me feel more alert, less irritable, and generally “on it” throughout the day.
The Bottom Line: Your Health, Your Energy
If you’re constantly tired, struggling to focus, or just feel “off,” don’t ignore it—B12 might hold the key. Start with a blood test, tweak your diet, and explore supplements if needed.
Getting your B12 levels right can be transformative:
More energy to keep up with work, family, and life.
Better mood and focus—less brain fog, more clarity.
Long-term health benefits for your heart, brain, and body.
Your energy is worth it. Start small, make one change, and see how much better you feel.
If you found this helpful, share it with someone who might need a little boost! Let’s make thriving—not just surviving—the new normal.
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