Drug and nutrient evidence
Medicines and nutrient status:separate established risks from broad depletion claims.
Some medicines can affect nutrient status, but the evidence differs by drug and patient. The safest approach is medicine-specific: identify a plausible risk, test when the result can change care, and avoid universal supplement lists.
Some medicines can affect nutrient status, but 'drug-induced depletion' is not one universal effect.
Medicine-nutrient relationships vary by drug, dose, treatment duration and patient risk. Some are well established. Others are associations with uncertain clinical importance.
Metformin is a clear example. The MHRA states that metformin can commonly reduce vitamin B12 levels and advises testing when deficiency is suspected, with periodic monitoring considered in people with risk factors. [1]
Long-term proton pump inhibitor use is another example where specific risks are recognised. The MHRA advises considering magnesium measurement before and during prolonged PPI treatment in relevant patients because hypomagnesaemia has been reported. [2]
Why is the word 'deplete' sometimes misleading?
'Deplete' can sound as if every person taking a medicine will lose the same nutrient and therefore needs a supplement. That is rarely a safe assumption.
A medicine may reduce absorption, alter metabolism, increase losses or simply be associated with a lower level in some people. The effect may depend on dose, duration, diet, age, kidney function or another condition.
The useful question is whether the medicine creates a clinically important risk in this person and whether testing or treatment would change care.
Use evidence by drug class, not one long depletion list.
Metformin and vitamin B12 have regulatory guidance. Long-term PPI therapy has recognised magnesium risk and may be associated with other nutrient changes, but the monitoring decision is still individual.
Statins are often linked online with coenzyme Q10 claims, yet NICE advises not offering CoQ10 to improve statin adherence. [3]
These differences show why a single chart of medicines and 'their nutrients' can overstate certainty.
Who may benefit from testing?
Testing is more useful when symptoms fit the deficiency, when treatment is prolonged, when the person has other risk factors, or when a regulator or guideline specifically recommends monitoring.
For metformin, the MHRA advises checking vitamin B12 when deficiency is suspected and considering periodic monitoring in people with risk factors. [1]
For PPIs, the MHRA advises considering magnesium measurement around prolonged treatment, particularly when other medicines can also lower magnesium. [2]
The testing guide explains why laboratory testing should follow a defined question.
Do not stop a useful medicine because of a nutrient concern.
Many medicine-associated nutrient problems can be investigated and treated without stopping the medicine. The MHRA specifically advises continuing metformin while vitamin B12 deficiency is corrected, as long as metformin is tolerated and not contraindicated. [1]
If a medicine may be contributing to a problem, review the benefit of the medicine, the seriousness of the deficiency and the available alternatives with the prescriber.
Stopping treatment without review can create more harm than the nutrient issue you are trying to solve.
What should a medicine and nutrient review include?
Bring the medicine name, dose, duration and reason it was prescribed. Add over-the-counter medicines and supplements.
Review symptoms, diet, previous results and other conditions that may affect the same nutrient. A low vitamin B12 level, for example, can have more than one cause.
Then decide whether the next step is testing, dietary change, supplementation, medicine review or no action.
- Do not assume every medicine on an internet list causes deficiency.
- Do not add a supplement before checking dose and interaction risk.
- Use the regulator or guideline for the specific medicine where one exists.
- Reassess if symptoms change or treatment duration becomes longer.
A practical way to interpret online nutrient-depletion charts.
Treat them as prompts for questions, not as prescribing guides. Check whether the source distinguishes strong evidence from weak associations and whether it explains who was studied.
Look for medicine-specific guidance from the MHRA, NICE, NHS or another authoritative source. If the chart jumps straight from an association to 'everyone should supplement', the conclusion is too broad.
Personal testing or supplementation should be tied to an individual risk or clinical question.
Use a four-step check for a medicine and nutrient claim
First, name the medicine. Broad claims such as 'medicines drain nutrients' are too vague to guide care. The evidence must match the drug or drug class.
Second, name the nutrient and the known effect. Is there a regulator warning, a guideline or strong research? Or is the claim only an association seen in some studies?
Third, check your own risk. Dose, treatment length, diet, age, gut disease and other medicines can all change the chance of a low level.
Fourth, ask what action follows. The answer may be a blood test, food advice, a supplement, a medicine review or no change. Do not add a product just because a chart links two words.
Keep the medicine benefit in view. A useful medicine should not be stopped because of an unconfirmed nutrient theory.
If a deficiency is found, treat the deficiency and review why it happened. The medicine may be one part of the explanation rather than the whole cause.
Three medicine examples show why one rule does not fit all
Metformin has clear advice on vitamin B12. The MHRA tells clinicians to test when deficiency is suspected and to consider periodic checks in people with risk factors.
Long-term PPI treatment has a different issue. Low magnesium has been reported, so the MHRA advises considering magnesium checks in people on prolonged treatment, especially when other medicines can also lower magnesium.
Statins are different again. NICE does not advise CoQ10 or vitamin D simply to help people stay on statin treatment. That is a reminder that an association is not the same as a routine supplement recommendation.
These examples are useful because they lead to different actions. One may lead to a blood test. Another may lead to medicine review. Another may lead to no supplement at all.
That is why the safest approach is drug-specific. Check the evidence for the actual medicine you take.
Bring the time line, not just the result
Write down how long you have taken the medicine and when symptoms began. Add major dose changes. Bring older results if the same nutrient was checked before.
This helps the clinician judge whether the medicine is a likely contributor, one of several factors, or not related at all.
Keep the diagnosis in view. A low nutrient level may need treatment, but the original medicine may still be important for controlling the condition it was prescribed for.
Use the medicine leaflet and the regulator as a starting point
Read the patient leaflet for the drug you take. It lists known side effects and key warnings. Then check current NHS, NICE or MHRA advice when a nutrient risk is claimed.
Ask your pharmacist if the claim is unclear. A pharmacist can help tell the difference between a known medicine effect and a weak online claim.
Do not buy a supplement just because the nutrient name appears next to your drug on a chart. First ask if you are at risk and if a test or treatment is needed.
What patients say about the consultation experience.
Patient reviews can help you understand how a consultation feels. They do not prove that a supplement, test or treatment is effective, and they do not predict a clinical outcome.
Individual reviews reflect personal experiences and do not predict diagnosis, treatment response or outcome.
“patient, understanding and kind”
Google reviewer
“warm and compassionate bedside manner”
Google reviewer
“takes incredible care to get to know her patients”
Google reviewer
Common questions
Can prescription medicines cause nutrient deficiencies?
Some can affect nutrient status, but the effect depends on the medicine and the person. Metformin and vitamin B12 are a well-established example, while other medicine-nutrient claims are weaker or more context-dependent. Do not assume every medicine causes a predictable deficiency.
Does metformin lower vitamin B12?
Yes. The MHRA states that metformin can commonly reduce vitamin B12 levels and that risk increases with higher doses, longer treatment and existing risk factors. It advises testing when deficiency is suspected and considering periodic monitoring in people at risk. [1]
Can proton pump inhibitors affect nutrients?
Long-term PPI use has recognised associations, including hypomagnesaemia. The MHRA advises considering magnesium measurement before and during prolonged treatment in relevant patients. The decision to test other nutrients depends on symptoms and individual risk rather than a universal panel. [2]
Should everyone on long-term medicines take supplements?
No. A supplement should have a reason. Test or supplement when there is a recognised risk, a confirmed deficiency or another evidence-based indication. Unnecessary supplements can create interactions, duplicated doses and cost without improving health.
Should I stop a medicine if a nutrient level is low?
Do not stop prescribed treatment on your own. Some deficiencies can be corrected while treatment continues. The MHRA specifically advises continuing metformin while vitamin B12 deficiency is corrected when metformin remains appropriate. Discuss the balance with the prescriber.
How do I know whether a drug-nutrient claim online is reliable?
Look for medicine-specific guidance from an authority such as the MHRA, NICE or NHS. Check whether the source separates proven adverse effects from associations and whether it explains who needs testing. Be cautious when a chart recommends the same supplement for everyone taking a medicine.
Medical sources and further reading
- MHRA: Metformin and reduced vitamin B12 levels. Provides medicine-specific advice on B12 risk, testing and continuing metformin.
- MHRA: Proton pump inhibitors and hypomagnesaemia. Provides safety advice on magnesium monitoring with prolonged PPI treatment.
- NICE NG238: Cardiovascular disease risk assessment and reduction. Includes the recommendation not to offer CoQ10 or vitamin D simply to improve statin adherence.
- NICE NG5: Medicines optimisation. Supports structured review of medicines, complementary products, safety and monitoring.
Use medicine-specific evidence, not a generic depletion chart.
Review the medicine, the nutrient risk and the reason for testing together before adding supplements or changing treatment.