product of creatine. That may complicate interpretation of certain kidney blood tests.
Therefore, people with known kidney disease should discuss creatine supplementation with a healthcare professional rather than assuming that a bodybuilding supplement is automatically appropriate for them.
## Why Dose Matters So Much
Many nutrients follow a simple principle:
**The dose makes the difference.**
A vitamin that is essential in normal amounts can become harmful when taken in enormous amounts.
For example:
* normal vitamin A intake supports health, while excessive preformed vitamin A can injure the liver
* vitamin D is essential, but extreme supplementation can raise calcium and damage the kidneys
* iron corrects iron deficiency, but excess iron can damage organs
* niacin is a vitamin at normal dietary doses but acts more like a medication at high doses
This is why supplement labels should never be interpreted as meaning that taking several times the recommended amount will produce greater benefits.
