Does eating a lot of protein harm your kidneys?

Short answer

Not if your kidneys are healthy. More protein makes the kidneys filter more, but kidney function did not decline over 10 years of follow-up, or after a year above 230 g a day for a 70 kg (154 lb) person. It is a different story if you already have kidney disease.

Does eating a lot of protein harm your kidneys?
'More protein → overworked kidneys → kidney damage' — does this formula hold?
A common claim: eat lots of protein to build muscle and your kidneys get overworked and break down. We checked this formula one step at a time.
Do the kidneys work harder on more protein?
Yes, they filter more
An analysis that pooled 30 studies with 2,160 people found that on high-protein diets, the amount the kidneys filter per minute rose by about 7 mL more on average. The first link, 'the kidneys work harder', is true.
Is working harder the same as damage?
Comparing changes, there was no difference
An analysis of 28 trials with 1,358 people found that the change in kidney function from before to after was the same with high and normal protein intake. A 2026 analysis of 22 trials also found no consistent sign of kidney damage.
What about eating it for years?
Over 10 years, kidney function did not fall faster
In 1,324 people whose kidney function was measured directly with a tracer drug and followed for a median of 10 years, more protein was not linked to faster decline. A study of 1,624 people with normal kidneys over 11 years found the same.
What if you eat far more?
No harmful changes over a year
14 people spent 6 months of 1 year eating as usual and 6 months eating more protein. For a 70 kg (154 lb) person, that is going from about 176 g to 232 g a day, and there were no harmful changes in kidney or liver markers or blood fats.
But weakened kidneys are different
Here, more protein was worse
In people whose kidney function was already slightly reduced, every extra 10 g of protein a day meant a larger drop in kidney function over 11 years. In data from 1,441 people with kidney disease, those eating under 70 g a day at 70 kg had a 23% lower risk of outcomes like dialysis or death.
Bottom line: protein did not damage healthy kidneys
The formula breaks at 'overworked → damaged'
More protein makes the kidneys filter more, but in healthy kidneys this did not lead to damage. Studies where a 70 kg person ate about 100 to 230 g a day showed no harmful results. If you have kidney disease, staying within the amount set with your doctor works.