Bone in CKD Alkali Response (BICARb Pilot Trial)

Inclusion Criteria (Pediatric Inclusion): * Children 5-17 years old * Estimated eGFR \>30 and \<90 ml/min/1.73m2 by CKiD U25 equations * Females of child-bearing potential must have had a menstrual period in the last month * Levels of PTH and alkaline phosphatase within 2x normal range and phosphorus within the normal range for age (per local laboratory reference assay) * 25-hydroxy Vitamin D ≥ 20 ng/mL * Females of child-bearing potential must be willing to use one form of effective contraception over the course of the study * Proficiency in English or Spanish * For participants \< 18 years, the participant and/or parent/guardian capable of providing informed consent and assent (assessed by the provider) Inclusion Criteria (Adult Inclusion): * Adults ≥ 18 years old * Estimated eGFR \>30 and \<90 ml/min/1.73m2 by the new CKD-Epi without race * Pre-menopausal women of childbearing age must have had a menstrual period in the last month * Levels of PTH and alkaline phosphatase within 2x normal range and phosphorus up to 5.0 mg/dL (per local laboratory reference assay) * Levels of 25-hydroxy Vitamin D ≥ 20 ng/mL * Women of childbearing potential must be willing to use one form of effective contraception over the course of the study * Proficiency in English or Spanish Exclusion Criteria (Pediatric and Adult): * Baseline potassium ≥ 5.5 mEq/L or prior history of hyperkalemia in the last 6 months (potassium \> 5.5 mEq/L) or currently taking a potassium lowering agent * Alkali therapy within the prior 12 months * Baseline ECG with abnormalities associated with increased risk of arrythmia, excluding left ventricular hypertrophy * Baseline serum bicarbonate levels \< 17 or ≥ 30 mEq/L * Serum calcium \< 8.6 mg/dL, adjusted for serum albumin * Significant comorbidity causing acid-base imbalance (e.g., active cancer requiring chemotherapy, chronic liver failure, moderate or severe chronic obstructive lung disease, New York Heart Association class 2 or greater congestive heart failure, obstructive sleep apnea requiring nightly continuous positive airway pressure, active glomerular disease requiring immunosuppressive therapy, intestinal malabsorption or celiac disease) * Plans to relocate out of the area in the next 3 months * Urine pH \> 8 or history of nephrolithiasis * Lower extremity amputations or non-ambulatory * Metabolic bone disease not related to CKD (e.g., Paget's disease, primary hyperparathyroidism) * Endocrinopathy: untreated hyper or hypothyroidism, Cushing's syndrome * Medical diseases that can affect therapy (severe myocardial damage, acute dehydration, delayed gastric emptying, esophageal compression, or intestinal obstruction or stricture) * Use of bisphosphonates, denosumab, teriparatide, abaloparatide, romosozumab, raloxifene, estrogen or testosterone replacement therapy, or an unstable dose of glucocorticoids within the 12-months prior to enrollment * Previous bilateral wrist and tibia fractures * Solid or liquid organ transplant * On dialysis or with rapidly deteriorating kidney function or expectation for transplantation or initiation of dialysis in less than 3 months * Pregnancy or breastfeeding * Prisoners or institutionalized individuals * Unwillingness to provide informed consent