Here are the medications most commonly discussed.
1. Metformin (for type 2 diabetes)
This is one of the most important medication-B12 interactions, especially in adults over 60.
What happens?
Metformin can reduce your body’s ability to absorb vitamin B12 from food and supplements.
Over time, this may lead to:
- B12 deficiency
- Anemia
- Numbness or tingling in the hands and feet
- Difficulty walking
- Memory problems
- Fatigue
- Depression
Why it matters after 60
Older adults already absorb less B12 because stomach acid naturally decreases with age. Combining aging with long-term metformin use significantly increases the risk of deficiency.
Should you stop taking B12?
No. In fact, many people taking metformin benefit from B12 supplementation.
Doctors often recommend:
- Checking B12 blood levels every 2–3 years (or sooner if symptoms develop)
- Taking oral B12 or receiving injections if deficiency is confirmed
There is no reason to avoid taking B12 with metformin. The issue is that metformin lowers B12 levels—not that B12 is harmful.
2. Acid-reducing medications
Examples include:
- Omeprazole
- Pantoprazole
- Esomeprazole
- Lansoprazole
(H2 blockers such as famotidine can also contribute, though typically to a lesser extent.)
What happens?
These medications reduce stomach acid.
Vitamin B12 from foods needs stomach acid to be released before it can be absorbed.
Long-term use may therefore reduce B12 absorption.
Possible symptoms
- Weakness
- Balance problems
- Tingling
- Memory issues
- Anemia
What should you do?
Again, do not stop B12.
Instead:
- Ask your healthcare provider whether your B12 level should be checked if you’ve used acid-suppressing medication for a long time.
- High-dose oral B12 or sublingual forms are often absorbed adequately even when stomach acid is reduced.
Other medications that can affect B12
Certain antibiotics (chloramphenicol)
Rarely used today, but it can interfere with the blood response to B12 treatment.
Colchicine
Used for gout.
Long-term use may reduce B12 absorption in some people.
Nitrous oxide (“laughing gas”)
Used during some surgeries and dental procedures.
It can temporarily inactivate vitamin B12, particularly in people who are already deficient.
Repeated exposure may worsen neurological symptoms.
Some seizure medications
Examples:
- Phenobarbital
- Primidone
- Phenytoin
These may alter vitamin metabolism, although clinically significant B12 deficiency is less common than with metformin.
Medications that should be separated from B12
These don’t usually require avoiding B12 entirely, but timing may matter.
Vitamin C (high doses)
Very large doses of vitamin C taken at the same time may reduce the amount of B12 available.
A practical approach is to take them at least 2 hours apart if using high-dose vitamin C.
Why B12 is especially important after age 60
Older adults are more likely to develop B12 deficiency because of:
- Reduced stomach acid
- Less dietary intake
- Long-term medication use
- Digestive disorders
- Reduced absorption
Untreated deficiency can lead to:
- Irreversible nerve damage
- Memory impairment
- Balance problems and falls
- Anemia
- Fatigue
Good dietary sources of B12
- Beef
- Fish
- Salmon
- Tuna
- Eggs
- Milk
- Yogurt
- Cheese
- Fortified breakfast cereals
Who should consider B12 testing?
You may benefit from discussing B12 testing with your healthcare provider if you:
- Are over 60
- Take metformin long term
- Use proton pump inhibitors or H2 blockers for months or years
- Follow a vegan diet
- Have unexplained numbness or tingling
- Have memory changes
- Feel unusually tired
- Have unexplained anemia
Bottom line
The claim that you should “never take B12” with two common medications is misleading.
The two medication groups most often associated with B12 are:
- Metformin – it can lower B12 levels, so supplementation is often beneficial rather than harmful.
- Acid-reducing medications (such as omeprazole or pantoprazole) – they can reduce B12 absorption over time, making monitoring or supplementation appropriate.
For most adults over 60, vitamin B12 is safe and often important, especially if deficiency is present or the risk is high. The decision to supplement should take into account your medications, diet, symptoms, and, when appropriate, blood test results.