It gets harder to absorb nutrients as we age. Vitamin B12 is a common one to miss if you follow a plant-based or vegetarian pattern because it’s found mostly in animal foods and fortified products. Older adults, people taking certain medicines and anyone with gut conditions that affect absorption can also run low—at least 4% of people between 40 and 59 are lacking in the nutrient and even more are borderline.
You may be at higher risk if you take metformin or long-term acid-suppressing medicines, have had weight-loss surgery or live with a digestive disorder such as coeliac disease or inflammatory bowel disease.
Being too low in vitamin B12 may cause everything from extreme fatigue to wonky vision. Here, dietitians and science reveal telltale signs of a vitamin B12 deficiency. If the symptoms below sound familiar, ask your GP for a blood test.
Exhaustion
Feeling fatigued even when you’ve had enough sleep is one of the earliest signs you may be low in B12.
"Fatigue is one of the first signs of B12 deficiency,” says registered dietitian Lisa Cimperman. Your body relies on B12 to make red blood cells, which carry oxygen throughout the body. When there isn’t enough oxygen in your blood, you feel tired no matter how long you sleep.
Fatigue can point to many things though, so clinicians are usually tipped off when tiredness shows up with other symptoms.
Muscle weakness
If your muscles aren’t getting enough oxygen from red blood cells, they can feel weak or heavy. If the grocery bag suddenly feels like a tonne, low B12 could be part of the picture.
Tingling and numbness
B12 deficiency can trigger odd sensations such as numbness, tingling or “pins and needles.” These symptoms are linked to nerve irritation or damage. Because B12 helps the nervous system function properly, these sensations can be a signal that your levels are low.
Brain fog
Maybe you put your keys in the fridge or had to think hard to remember your niece’s name. You might worry about early onset dementia, but low B12 can also be to blame. The vitamin is crucial for healthy brain function and being deficient can leave you confused or forgetful.
“I’ve seen this deficiency mistaken for Alzheimer’s in elderly patients,” says Cimperman. “But once they have a blood test and it reveals a B12 deficiency, they start taking a supplement and their symptoms start to fade.”
Loss of balance
Feeling wobbly or dizzy is another common sign. Low B12 can irritate nerves, which may cause poor balance, reduced coordination or vertigo, research suggests.
Pale skin
If your complexion looks unusually pale or slightly yellow, low B12 could be the culprit. The vitamin helps you make red blood cells. When you’re deficient, the cells you do have can be fragile. As they break down they release bilirubin—a yellow pigment that can leave skin looking jaundiced.
Smooth, red tongue
About half of people with a severe B12 deficiency lose the papillae—the tiny bumps—on their tongue, especially around the edges. Because many papillae contain taste buds, foods may lose their appeal.
“Women with a B12 deficiency may actually lose weight because food doesn’t taste as good to them anymore,” says a dietitian Angela Grassi. Some also report burning or soreness, particularly on the back of the tongue.
Anxiety and depression
Feeling more down or on edge than usual can be another sign. “A lack of B12 wreaks havoc on your mood, possibly leading to depression or anxiety,” says Grassi.
The reason isn’t fully clear, but B12 helps synthesise brain chemicals like serotonin and dopamine that support stable mood.
Change in vision
In severe cases, low B12 may irritate the optic nerve or affect blood vessels in the retina, which can lead to blurry or double vision, light sensitivity and even vision loss, research suggests. If you notice any sudden change in vision, see your GP or optometrist promptly.
Newsletter
