Glycogen storage disease (GSD) type Ia (glucose-6-phosphatase deficiency) and Ib (glucose-6-phosphate transporter deficiency) are both clinically characterized by fasting hypoglycaemia and hepatomegaly. Chronic kidney disease (CKD) with loss of glomerular filtration rate and albuminuria/proteinuria is a known long-term complication of GSD I that has become less frequent with improvement of therapy over the last decades. We retrospectively investigated a cohort of 63 GSD I patients (51 GSD Ia, 12 GSD Ib, mostly adults) with a mean age of 27.8 ± 1.8 years. We performed a cross-sectional analysis of renal function, metabolic parameters, co-morbidities and medication at the time of last-follow-up. Our study shows that renal complications have become less common since standardized diet and renoprotective medications are available. CKD was only evident above the age of 25 years in our cohort and the decline in glomerular filtration rate was moderate. No patient required renal replacement therapy. Renal calcifications and kidney stones were no frequent complications. Insufficient metabolic control was a potential risk factor for proteinuria. Supportive therapy with angiotensin-converting enzyme inhibitors is not regularly used in patients suffering from (micro-) albuminuria. This study reveals that with adherence to a standardized diet and renoprotective medication, renal complications in GSD I occur later and are less severe. However, renal involvement occurs at a similar frequency to GSD cohorts studied about 20 years earlier. Since micro-albuminuria in GSD increases the risk of progression of renal disease to kidney failure, a thorough characterization of larger GSD cohorts and a better understanding of underlying pathomechanisms are needed to minimize kidney involvement in GSD I.