BackgroundIn the UK, the majority of patient contact with health services occurs in primary care. Most of these contacts are uncomplicated; however, patient safety incidents (eg, failure to recognise patient deterioration) can occur. We aimed to explore patient and health-care factors associated with a self-referred admission, in patients with deteriorating health who consulted a general practitioner (GP). MethodsIn this observational study, we identified patients who had consulted a GP in the 3 days before an unplanned admission (indication of deterioration) between April 1, 2014, and Dec 31, 2017, in England, using the Clinical Practice Research Datalink with linkage to inpatient hospital admissions and emergency department data. We applied a multivariable, multilevel logistic regression model (generalised estimating equations) to investigate factors associated with self-referral (ie, patient age and existing health conditions, GP consultation, deteriorating health condition, and previous health service use) compared with other-referred unplanned admissions (eg, GP-referrals). Self-referred admission, as a composite measure, was defined as an unplanned admission via the emergency department (inpatient data) recorded as a self-referral in the corresponding emergency department record. We investigated all diagnoses and a subset of commonly reported missed conditions: sepsis, pulmonary embolism, urinary tract infections, and ectopic pregnancies in women. FindingsOf 405 878 unplanned admissions, 116 094 (28%) patients had contact with a GP 3 days before admission. The proportion of self-referred admissions varied by region (4189 [31%] of 13 639 inpatient admissions in London vs 1721 [12%] of 14 641 inpatient admissions in south west England), age, deteriorating health, and existing health conditions. Patients with sepsis or a urinary tract infection were more likely to self-refer than patients with other conditions (adjusted odds ratio [OR] 1·10, 95% CI 1·02–1·19 for sepsis; 1·09, 1·04–1·14, for urinary tract infection). GP appointment length was associated with a self-referred admission: a 5 min increase in consultation duration decreased the risk of self-referral by 6% (OR 0·94, 0·91–0·97). Telephone consultations, comorbidity, and previous health service use were also associated with self-referred admission. InterpretationDifferentiating deterioration from self-limiting conditions is difficult for GPs, particularly in patients with sepsis, urinary tract infections, or long-term conditions. The negative association between GP consultation duration and self-referral supports demand for longer GP consultations. However, more research is needed to investigate the underlying mechanism between GP consultation time and referral. FundingNational Institutes for Health Research.