Research on the relationship between ingestion of fluoride and renal function is limited by several factors including:

• Most of the studies were of neutral or negative methodological quality
• Few studies report precise individual levels of fluoride ingestion
• None of the studies were of U.S. populations.

The research suggests that ingestion of lower levels (conservatively, lower than 1 to 1.5ppm) of fluoride in healthy subjects is not associated with renal impairment.

The very limited research does suggest an association between ingestion of higher levels (2.2ppm in a single study, though there is no clear definition of "higher levels" obtainable from the research) of fluoride in drinking water and fluorotoxic effects in subjects with impaired renal function. However, the research suggests that this association may be the result of impaired fluoride excretion by subjects who already have some form of renal compromise.

• Grade I means there is Good/Strong evidence supporting the statement;
• Grade II is Fair;
• Grade III is Limited/Weak;
• Grade IV is Expert Opinion Only;
• Grade V is Not Assignable.
• High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
• Moderate (B) means we are moderately confident in the effect estimate;
• Low (C) means our confidence in the effect estimate is limited;
• Very Low (D) means we have very little confidence in the effect estimate.
• Ungraded means a grade is not assignable.