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Rationale & Objective: Estimates of the incidence of hyperkalemia in patients with chronic kidney disease (CKD) vary widely. Our objective was to estimate hyperkalemia incidence in patients with CKD from routine clinical care, including by level of kidney damage or function and among important patient subgroups. Study Design: Retrospective cohort study. Setting & Participants: 1,771,900 patients with stage 1-4 CKD identified from the US Optum De-Identified electronic health records database. Exposures or Predictors: Impaired kidney damage or function level at baseline based on urinary albumin-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR), respectively, and selected patient subgroups. Outcomes: Hyperkalemia: 2 elevated serum potassium values (≥5.5 mmol/L) from the inpatient setting (2-24 hours apart) or outpatient setting (maximum 7 days apart), or 1 elevated serum potassium value plus pharmacotherapy initiation or hyperkalemia diagnosis (maximum 3 days apart). Analytical Approach: Incidence rates of hyperkalemia were calculated. Estimates were stratified by UACR and eGFR level at baseline and patient subgroups. Results: Over a mean follow-up of 3.9 years, the incidence of hyperkalemia was 3.37 events/100 person-years (95% confidence intervals, 3.36-3.38). Higher incidence rates were observed with increased UACR and lower eGFR. Highest rates were observed with UACR ≥3,500 (up to 19.1/100 person-years) irrespective of decreased eGFR level. High rates also occurred in patients with type 2 diabetes mellitus (T2DM, 5.43/100 person-years), heart failure (8.7/100 person-years), and those prescribed steroidal mineralocorticoid receptor antagonists (sMRAs, 7.7/100 person-years). Limitations: Potential misclassification of variables from possible medical coding errors; potential data incompleteness issues if patients received care at institutions not included in Optum. Conclusions: Hyperkalemia is a frequent occurrence in CKD, particularly in patients with T2DM, heart failure, or prescribed sMRAs, indicating the need for regular serum potassium and UACR monitoring in this patient population to help mitigate risk. Plain-Language Summary: People with chronic kidney disease (CKD) have a higher risk of illness, hospitalization, and death than those without CKD. Medicines that are commonly used to slow down CKD progression can sometimes lead to hyperkalemia, where levels of potassium in the blood are higher than normal and which can be potentially dangerous. Concerns about hyperkalemia have led some people with CKD to stop taking their medication. Our study of 1.7 million patients from the United States found that patients with severe kidney damage, as well as those with type 2 diabetes mellitus or heart failure, have a higher risk of hyperkalemia than other patients, indicating they are priority groups for having their potassium levels and level of kidney damage checked regularly.