Living kidney donation provides the best outcomes (survival, cost, and quality of life) of all renal replacement modalities. Living kidney donors, on the other hand, are at the increased risk of end-stage kidney disease (ESKD) after donation compared with healthy nondonors for multiple possible reasons. Extensive predonation screening is required to assess eligibility for donation to avoid the rejection of suitable candidates and minimize acceptance of donors with increased risk of ESKD. The association between the lower predonation glomerular filtration rate (GFR) and increased ESKD risk in donors highlights the relevance of GFR assessment for living kidney donor candidates. However, the method to evaluate GFR is still debated, and the thresholds of acceptable predonation GFR vary across guidelines. All guidelines favor GFR measurement with an exogenous tracer over estimated GFR, but only the British Transplant Society guidelines mandates it. While the Kidney Disease Improving Global Outcomes Group guidelines advocates for age-independent GFR thresholds, most other guidelines propose various age-dependent GFR thresholds with resulting profound differences in assessment of donor suitability between guidelines. Many important questions are not addressed by any guidelines, including the approach to discordant GFR measurement and estimated GFR results, the use of method-specific GFR thresholds and thresholds dependent on comorbidities or race. Further data are required exploring the associations between these variables and the course of postdonation GFR. Last, GFR evaluation studies conducted in approved donors and not in those initially presenting as potential candidates are questionable regarding their suitability for potential donor evaluation.