Glomerulonephritis is the second most common cause of end stage renal disease in the UK and the most common cause in those under 35. Some forms can respond well to treatment if diagnosed early. However, if glomerulonephritis goes unrecognised, it can lead to irreversible loss of renal function. Glomerulonephritis can present in a wide variety of ways, ranging from asymptomatic urinary abnormalities to fulminant disease with life-threatening acute kidney injury and extra-renal manifestations. Asymptomatic invisible haematuria is common. In the absence of infection or a urological cause, glomerulonephritis should be considered. Significant proteinuria (> 1 g/day) in the absence of an identifiable cause warrants referral.