Why magnesium and vitamin D deficiency go hand in hand
Low magnesium can directly cause or worsen low vitamin D — and the other way round. Magnesium is a cofactor (an essential helper) for the enzymes that activate vitamin D. Without enough magnesium, vitamin D stays in its inactive form and can’t do its job properly.
Research suggests that up to 50% of people with low vitamin D also have low magnesium, which makes vitamin D less effective. On top of that, vitamin D helps your gut absorb magnesium. The result is a loop: being low in one makes you lower in the other.
Vitamin D goes through several steps before it becomes active:
Vitamin D (cholecalciferol) from food or sunlight is converted in the liver into 25-hydroxyvitamin D by one enzyme. Then, in the kidneys, another enzyme turns it into the active form, 1,25-dihydroxyvitamin D. Both enzymes depend on magnesium.
Magnesium is also needed to bind vitamin D to its carrier protein in the blood, and to break down excess vitamin D so it doesn’t build up to harmful levels.
Low magnesium also reduces parathyroid hormone, which signals the kidneys to activate vitamin D. This is sometimes called “magnesium-dependent vitamin D resistance”.
Vitamin D, in turn, boosts magnesium absorption in the gut. If magnesium is low, vitamin D isn’t activated, its blood level drops, and that affects bone health, immunity and possibly inflammation.
What can you do?
Ask your GP about checking your vitamin D and magnesium levels (serum magnesium, and red blood cell magnesium if appropriate). If your results are low, work out next steps with your GP rather than self-treating.
Eat more magnesium-rich foods (almonds, spinach, avocado, pumpkin seeds, bananas) and vitamin D sources (oily fish, eggs, mushrooms, fortified foods).
Get a little sun. In Australia, check the daily UV index (for example, in the SunSmart app). When the UV index is below 3, a short time outdoors without sun protection is fine. When it’s 3 or above, use sun protection — in summer, a few minutes of everyday outdoor time is usually enough.
Want a plan that fits your body and your routine? Book a session →
General information only, not medical advice. If you have a health condition, please talk to your GP.
Research suggests that up to 50% of people with low vitamin D also have low magnesium, which makes vitamin D less effective. On top of that, vitamin D helps your gut absorb magnesium. The result is a loop: being low in one makes you lower in the other.
Vitamin D goes through several steps before it becomes active:
Vitamin D (cholecalciferol) from food or sunlight is converted in the liver into 25-hydroxyvitamin D by one enzyme. Then, in the kidneys, another enzyme turns it into the active form, 1,25-dihydroxyvitamin D. Both enzymes depend on magnesium.
Magnesium is also needed to bind vitamin D to its carrier protein in the blood, and to break down excess vitamin D so it doesn’t build up to harmful levels.
Low magnesium also reduces parathyroid hormone, which signals the kidneys to activate vitamin D. This is sometimes called “magnesium-dependent vitamin D resistance”.
Vitamin D, in turn, boosts magnesium absorption in the gut. If magnesium is low, vitamin D isn’t activated, its blood level drops, and that affects bone health, immunity and possibly inflammation.
What can you do?
Ask your GP about checking your vitamin D and magnesium levels (serum magnesium, and red blood cell magnesium if appropriate). If your results are low, work out next steps with your GP rather than self-treating.
Eat more magnesium-rich foods (almonds, spinach, avocado, pumpkin seeds, bananas) and vitamin D sources (oily fish, eggs, mushrooms, fortified foods).
Get a little sun. In Australia, check the daily UV index (for example, in the SunSmart app). When the UV index is below 3, a short time outdoors without sun protection is fine. When it’s 3 or above, use sun protection — in summer, a few minutes of everyday outdoor time is usually enough.
Want a plan that fits your body and your routine? Book a session →
General information only, not medical advice. If you have a health condition, please talk to your GP.
