B12 deficiency after 50 in NZ: signs, causes and what to do

Tired all the time? Foggy, forgetful, a bit low, or noticing pins and needles in your hands or feet? Vitamin B12 is one of the easiest things to overlook — and one of the easiest to put right once you know to look.

I’m Dr Roderick Mulgan, an Auckland GP and the founder of Lifeguard Health. This is a plain-English guide to B12 for New Zealanders over 50: why so many of us run low as we age, the signs worth taking seriously, and what to actually do about it.

The short version

B12 matters for energy, a healthy nervous system and making red blood cells. The catch after 50 is absorption: your body gets less efficient at pulling B12 out of food, so you can eat enough and still end up short. Add a common medication or two and the odds rise further. The good news is that it’s simple to check and simple to fix.

Why absorption drops after 50

To absorb B12 from food, your stomach needs enough acid to release it, plus a protein called intrinsic factor to carry it across the gut. Both tend to decline with age. On top of that, two of the most commonly prescribed medications in New Zealand interfere with B12:

• Reflux medications (proton-pump inhibitors like omeprazole) lower stomach acid, which reduces B12 absorption over time.
• Metformin, used for type 2 diabetes, is well known to lower B12 with long-term use.

None of this means you should stop a medication — it means B12 is worth keeping an eye on if you take them.

Who’s most at risk in NZ

• Adults over 50, simply through reduced absorption.
• Vegetarians and vegans — B12 occurs naturally only in animal foods.
• Anyone on long-term reflux medication or metformin.
• People with coeliac disease, Crohn’s, or who’ve had gut surgery.

The signs of low B12

This is the tricky part: the symptoms are vague and overlap with plenty of other things, including menopause and an underactive thyroid. They can include persistent tiredness, brain fog and poor concentration, low mood, a sore or smooth tongue, tingling or numbness in the hands and feet, and problems with balance. Because they creep up slowly, they’re easy to put down to “just getting older”.

The nerve-related symptoms in particular are worth acting on, because prolonged deficiency can cause damage that’s harder to reverse. If you have persistent tingling, numbness or balance problems, see your GP.

Food, or a supplement?

B12 comes from animal foods — meat, fish, eggs and dairy — and in New Zealand most meat-eaters get enough in their diet. The issue after 50 is usually absorption, not intake, which is why a perfectly good diet doesn’t always solve it.

If you eat little or no animal food, a reliable B12 supplement isn’t optional — it’s essential, because there’s no meaningful plant source. And if absorption is the problem, an oral supplement can still help, because some B12 is absorbed passively (without needing stomach acid or intrinsic factor) when the dose is high enough. For genuine, diagnosed deficiency, though, your GP may recommend injections.

What to do

The sensible path is simple:

• If you’re in a risk group or have the symptoms, ask your GP for a blood test. It takes the guesswork out.
• If you’re low, your GP will advise the right approach — a high-dose oral supplement, or injections for more significant deficiency.
• If you’re fine but want to stay topped up — especially as a vegetarian or vegan, or if you’re on metformin or reflux medication — a daily B12 supplement is a reasonable maintenance step.

Where Lifeguard fits

I’ll be straight with you: Lifeguard doesn’t make a standalone B12, and I’m not going to pretend otherwise. If you need B12 specifically, the guidance above — diet, a dedicated B12 supplement, and your GP for anything diagnosed — is the right path.

Where our range fits is your broader daily foundation for healthy ageing. Lifeguard Essentials is our doctor-formulated daily base for adults 45+, and the Lifeguard Bundle pairs it with our other core formulas. For more, see our healthy ageing supplements guide and our companion guide on vitamin D for over-50s in NZ, another nutrient many Kiwis are short on.

A supplement supports good nutrition — it isn’t a substitute for medical care. Diagnosed B12 deficiency is a medical matter: see your GP for testing and treatment.

Frequently asked questions

What are the signs of B12 deficiency over 50?

They’re vague and build slowly: persistent tiredness, brain fog, low mood, a sore tongue, and tingling or numbness in the hands and feet. Because they overlap with other conditions, a blood test is the way to confirm it. See your GP about persistent nerve symptoms.

Why does B12 absorption decrease with age?

Absorbing B12 from food needs stomach acid and a protein called intrinsic factor, and both decline with age. That’s why some over-50s run low even on a good diet.

Can metformin or reflux medication cause low B12?

Yes. Long-term metformin and proton-pump inhibitors (reflux medications) both reduce B12 over time. Don’t stop a prescribed medication; ask your GP to check your B12.

Do I need a B12 supplement after 50?

Not everyone does. Most meat-eaters get enough in their diet, but vegetarians and vegans, and anyone on metformin or reflux medication, are more likely to benefit. A blood test will tell you where you stand.

Should I get my B12 levels tested?

If you’re in a risk group or have the symptoms, yes. It’s a simple blood test through your GP, and it removes the guesswork before you start supplementing.

Written by Dr Roderick Mulgan, NZ GP and founder of Lifeguard Health. This article is general information, not medical advice. For testing or treatment of a B12 deficiency, see your GP.