How it harms
High vitamin D → hypercalcaemia (too much calcium in blood) → deposition of calcium in renal tubules → kidney stones, nephrocalcinosis, impaired kidney function.
Liver: excessive vitamin D means higher workload in the liver for metabolising, and calcium overload can harm hepatic microcirculation. Also, fat-soluble vitamins in excess generally burden the liver.
Key risk factors
High‐dose supplementation without monitoring (e.g., > 4,000 IU/day for adults unless supervised).
Poor kidney function (makes dealing with calcium harder).
Using vitamin D plus high calcium intake or other supplements that raise calcium.
How to protect yourself
Get your vitamin D blood level measured before high-dose use.
Use only the dose recommended by your doctor.
Monitor calcium, kidney function, and watch for kidney stone history.
3. Iron Overload (Excess Iron Supplementation)
What it is
Iron is essential but supplementing when not needed can cause “iron overload”.
How it harms
The liver stores excess iron (in ferritin/hemosiderin). Over time this can cause liver inflammation, fibrosis, cirrhosis.
Kidneys: Iron excess creates oxidative stress and may damage glomeruli or tubules; though less directly, overload conditions can affect kidney structure.
Key risk factors
Taking iron supplements without iron deficiency or doctor supervision.
Genetic conditions like haemochromatosis (iron-storage disease).
How to protect yourself
Test ferritin and transferrin saturation before supplementing iron.
Avoid taking iron when not needed.
