The outcomes and experience of care for patients who start renal replacement therapy (RRT) in an unplanned manner are worse than for those who have planned care. The objective of this study was to examine the primary care predictors of unplanned starts to RRT.Retrospective cohort study with linked primary care and hospital data.128 general practices in East London with a combined population of 1 043 346 people.999 consecutive patients starting dialysis at Barts Health National Health Service Trust between September 2014 and August 2017.Unplanned versus a planned start to dialysis among the cohort of 389 patients with a linked primary care record. An unplanned start to dialysis is defined as receiving nephrology care in the low clearance clinic (or equivalent) for less than 90 days. A planned start is defined as access to pre-dialysis counselling and care for at least 90 days prior to commencing dialysis.The adjusted logistic regression analysis showed that the most important modifiable risk factors for unplanned dialysis were the absence of a chronic kidney disease (CKD) code in the general practice (GP) record (OR 8.02, 95% CI 3.65 to 17.63) and the absence of prescribed lipid lowering medication (OR 2.37, 95% CI 1.05 to 5.34). Other contributing factors included male gender and a greater number of long-term conditions.Improving CKD coding in primary care and the additional review and clinical scrutiny associated with this may contribute to a further reduction in unplanned RRT rates.