11 Signs of a Vitamin B12 deficiency
Feeling tired, foggy, or low in mood even though your diet looks “fine”?
Vitamin B12 deficiency is far more common than most people realise.
And for many, the issue isn’t intake, it’s absorption.
What Is Vitamin B12 and Why Does It Matter?
Vitamin B12 is an essential nutrient your body relies on every single day.
It plays a key role in:
- Making red blood cells
- Supporting your nervous system
- Producing DNA
- Regulating energy metabolism in every cell
Without enough B12, these systems don’t work properly.
When that happens, symptoms can show up quietly and worsen over time.
Why B12 Deficiency Is So Common
Vitamin B12 is classed as an essential nutrient.
Your body cannot make it. You must get it from food or supplementation.
While B12 can be stored in the liver, absorption is inefficient for many people, and unused B12 is excreted. This means consistent intake and effective absorption both matter.
Deficiency is surprisingly common, and diet alone does not explain it¹.
What causes a Vitamin B12 deficiency?
1. Diet Is Only Part of the Story
Vitamin B12 is found mainly in animal foods, which is why vegans and vegetarians are at higher risk of deficiency.
However, B12 deficiency also occurs in people who eat meat.
The amount of B12 in animal foods varies depending on the animal’s diet, supplementation practices, and how often those foods are eaten. Many people simply don’t consume B12-rich foods regularly enough to maintain stable levels.
2. Absorption Declines With Age
As we age, stomach acid production often decreases.
Stomach acid is required to release B12 from food proteins.
Less acid = less absorption.
This is one reason adults over 50 are significantly more likely to have low B12 levels³.
3. Medications & Health Conditions
Certain medications interfere with B12 absorption.
Metformin, commonly prescribed for type 2 diabetes, is a well-documented example².
Digestive conditions affecting the stomach or intestines can also reduce how much B12 reaches the bloodstream.
If you suspect a deficiency, speak to a healthcare professional. Blood testing is simple, and treatment is highly effective when started early.
What are the symptoms of a B12 deficiency?
You don’t need to be severely deficient to feel symptoms. Even borderline low levels can affect how you feel.
Energy & Fatigue
- Persistent tiredness
- Weakness
- Shortness of breath
B12 is essential for healthy red blood cell production. When levels fall, oxygen delivery around the body suffers³.
Lack of concentration:
- Brain fog or poor concentration
- Headaches or migraines
- Low mood or depressive symptoms
Low B12 is linked to higher homocysteine levels, which contribute to oxidative stress and neurological damage⁶.
Nerves & Physical Symptoms
- Pins and needles
- Balance or coordination issues
- Muscle weakness or cramps
Long-term deficiency can damage nerves, affecting both sensory and motor function³⁹.
Other Physical Signs
- Pale or yellowing skin³
- Digestive discomfort, including nausea, bloating, constipation, or diarrhoea³
- A swollen, sore, or shiny tongue (glossitis)⁸
- In men, elevated homocysteine associated with B12 deficiency may impair blood flow, contributing to erectile dysfunction⁷.
How Long Does It Take to Recover?
Recovery depends on the cause.
- Diet-related deficiency may require short-term high-dose supplementation or injections
- Absorption-related deficiency may require ongoing supplementation
Many people notice improvements in energy and focus relatively quickly once B12 intake is restored.
However, leaving deficiency untreated for too long increases the risk of permanent nerve damage³.
Why Your B12 Supplement Might Not Be Working:
Vitamin B12 tablets must survive digestion first.
They rely on:
- Adequate stomach acid
- Functional intrinsic factor
- A healthy digestive tract
Age, medications, and gut issues can all reduce how much B12 is actually absorbed³.
Liquid B12 taken under the tongue (sublingually) bypasses much of the digestive process, allowing B12 to enter the bloodstream more directly. This makes it a practical option for people concerned about absorption efficiency.
Who Should Pay Closer Attention to B12?
You may want to be especially mindful of your B12 intake if you:
- Follow a plant-based diet
- Are over 50
- Take metformin or acid-reducing medication
- Experience persistent fatigue, brain fog, or neurological symptoms
A Practical Way to Support B12 Intake
Vivo Life’s Liquid B12 contains three active forms of vitamin B12 and is taken under the tongue.
This means it doesn’t rely as heavily on digestion, which can be helpful if you’re worried your body isn’t absorbing B12 as well as it should.
References
-
Vitamin B12 deficiency prevalence and causes — Gana et al., Nutrients, 2021
https://www.mdpi.com/2072-6643/13/2/479 -
Metformin-associated vitamin B12 deficiency — de Jager et al., BMJ, 2010
https://www.bmj.com/content/340/bmj.c2181 -
Vitamin B12 deficiency: clinical overview — Ankar Kumar, StatPearls, 2019
https://www.ncbi.nlm.nih.gov/books/NBK441923/ -
Vitamin B12 and cognitive function in ageing — Nalder et al., Nutrients, 2020
https://www.mdpi.com/2072-6643/12/3/678 -
Vitamin B12 levels and migraine prevalence — Togha et al., Headache, 2019
https://pubmed.ncbi.nlm.nih.gov/30810214/ -
Homocysteine, vitamin B12, and depression — Young et al., Journal of Psychiatric Research, 2019
https://pubmed.ncbi.nlm.nih.gov/30753423/ -
Vitamin B12 deficiency and erectile dysfunction — Xu et al., Andrologia, 2021
https://pubmed.ncbi.nlm.nih.gov/33550662/ -
Oral signs of B-vitamin deficiency — Kobayashi & Iwasaki, Nutrients, 2020
https://www.mdpi.com/2072-6643/12/8/2359 -
Neuromuscular effects of vitamin B12 deficiency — Wolffenbuttel et al., Nature Reviews Endocrinology, 2019
https://www.nature.com/articles/s41574-019-0265-0 -
Metformin, diabetes, and neuropathy risk — W et al., Diabetes Care, 2019
https://pubmed.ncbi.nlm.nih.gov/30622032/