Magnesium quietly powers more than 300 enzyme reactions in the body, helps regulate blood pressure, and is increasingly studied as a factor in vascular calcification — a major problem in CKD. So is supplementing it sensible? In the UK, the answer is "sometimes, with care".
UK reference intakes
The UK Reference Nutrient Intake (RNI) for magnesium in adults is around 300 mg/day for men and 270 mg/day for women. Good food sources include wholegrains, nuts, seeds, leafy greens, beans and oily fish.
Magnesium and the kidneys
Healthy kidneys are excellent at clearing excess magnesium. In CKD, that ability falls and blood magnesium can rise, especially with magnesium-based laxatives or antacids (such as some "milk of magnesia" products). Symptoms of high magnesium include nausea, weakness, low blood pressure and, at extreme levels, heart-rhythm problems.
What about deficiency?
Some diuretics, prolonged diarrhoea and proton pump inhibitors (omeprazole, lansoprazole) can lower magnesium. Your GP can check a blood level if symptoms suggest it.
Practical advice
- Aim to get magnesium from food first.
- If you have CKD, avoid magnesium-based laxatives and antacids unless your renal team approves.
- Be cautious with high-strength magnesium supplements (above 400 mg elemental magnesium).
- If you are on long-term PPIs, ask your GP whether to monitor magnesium.
Bottom line
Magnesium is essential, but in CKD the margin between "useful" and "too much" is narrower. Food first, supplements only with advice.