You take a medication. You take it every day, possibly for years. Nobody mentions that it is quietly depleting a nutrient your body needs. The depletion builds gradually. Symptoms emerge — fatigue, muscle weakness, low mood, poor memory. You see your GP. They run tests. The nutrient isn't checked. You leave with a second prescription.
This is not a rare scenario. It is the routine experience of a significant proportion of people on long-term medication in the UK.
How drug-nutrient depletion works
Medications affect nutrient status through several mechanisms. Some drugs compete directly with nutrients for absorption — metformin, for example, blocks the active transport system in the gut that B12 uses to enter the bloodstream. Others increase urinary excretion: loop diuretics cause the kidneys to flush magnesium, zinc, potassium, and calcium. Some deplete nutrients through increased metabolic demand — the body uses more of a specific cofactor to metabolise the drug, depleting the reserve over time.
The clinical problem is timing. These depletions are dose-dependent and cumulative. A patient who has been on a statin for two years has a meaningfully different CoQ10 status than one who started last month. The symptom connection — muscle pain, fatigue, exercise intolerance — is rarely made because nobody drew the line between the prescription and the depletion.
The most clinically significant interactions
Statins → CoQ10
Statins inhibit the HMG-CoA reductase enzyme — the same pathway the body uses to synthesise CoQ10. CoQ10 (ubiquinol) is essential for mitochondrial energy production. Every cell that generates energy requires it. Statin-induced CoQ10 depletion is well-documented in the literature and explains the muscle pain, fatigue, and exercise intolerance that a significant minority of statin users experience. Supplementation with ubiquinol 100–200mg daily is standard in functional medicine practice for any patient on long-term statin therapy.
Metformin → Vitamin B12
Metformin reduces B12 absorption through competitive inhibition of calcium-dependent membrane receptors in the gut. B12 deficiency on metformin is dose-dependent, progressive, and significantly underdiagnosed. The clinical consequence — peripheral neuropathy, cognitive decline, fatigue, elevated homocysteine — is often attributed to diabetes progression rather than the medication causing the deficiency. NICE recommends monitoring B12 in long-term metformin users but this is inconsistently applied in practice.
PPIs → Magnesium, B12, zinc, iron
Proton pump inhibitors reduce gastric acid production. Gastric acid is required for the absorption of multiple nutrients — particularly magnesium, B12, zinc, and non-haem iron. Long-term PPI use (beyond 12 weeks) consistently produces measurable reductions in all four. Magnesium depletion is the most clinically significant: hypomagnesaemia on PPIs can cause muscle cramps, cardiac arrhythmias, anxiety, and insomnia. The European Medicines Agency issued a warning about PPI-induced hypomagnesaemia in 2012 — yet monitoring remains rare in general practice.
Oral contraceptives → B6, B12, folate, zinc, magnesium
The combined oral contraceptive pill affects the metabolism and absorption of multiple B vitamins and minerals. B6 depletion is particularly significant — B6 (as P5P) is required for serotonin and dopamine synthesis, progesterone receptor sensitivity, and oestrogen detoxification. Low B6 on the pill contributes to the mood changes, low libido, and emotional blunting that many women experience — symptoms frequently attributed to the pill itself rather than to the downstream nutrient depletion it causes.
Corticosteroids → Calcium, vitamin D, zinc, magnesium
Long-term corticosteroid use reduces calcium absorption, increases urinary calcium excretion, and impairs vitamin D activation. This is well-recognised — steroid-induced osteoporosis is a documented clinical entity and calcium/vitamin D supplementation is standard of care. Less well-recognised is the zinc and magnesium depletion that accompanies prolonged steroid use, contributing to immune suppression and poor wound healing.
"When a patient on long-term medication presents with fatigue, muscle symptoms, or cognitive changes, the first question in functional medicine is not 'what new symptom is this?' — it's 'what is their medication depleting?'"
What to do with this information
This is not a case for stopping medication — statins, metformin, and PPIs save lives and manage serious conditions. It is a case for monitoring the nutritional consequences of long-term use and supplementing proactively where depletion is predictable.
If you are on any of the medications above, these are the functional medicine minimum checks worth requesting or running privately: B12 if on metformin or PPIs. Magnesium (ideally RBC magnesium) if on PPIs, diuretics, or corticosteroids. CoQ10 if on statins. B6, B12, and folate if on the oral contraceptive pill for more than two years.
The depletion is predictable. The monitoring is straightforward. The intervention — in most cases, targeted supplementation — is inexpensive. The compounding of symptoms that follows years of unaddressed depletion is neither.
Your prescription came with a patient information leaflet. It listed the side effects. It didn't mention what the medication was quietly taking away.