eGFR 30 to 44 mL/min/1.73m²

KDIGO labels 30 to 44 "Moderately to severely decreased." The definition of CKD is the same as at G3a, a GFR under 60 for at least 3 months, and the confirmation rules are the same: no chronicity from a single value, and a combined creatinine and cystatin C estimate where accuracy matters. What changes is risk. KDIGO's monitoring figure shows the step up: eGFR and ACR twice a year at A1 and three times a year at A2 and A3.

The risk equation. KDIGO recommends estimating the absolute risk of kidney failure at G3 to G5 with an externally validated equation (Recommendation 2.2.1, grade 1A); the one it tables is the Kidney Failure Risk Equation, built on age, sex, eGFR and ACR. A 5-year risk of 3 to 5 percent "can be used to determine need for nephrology referral," and the guideline says most people at lower risk "may be effectively managed in primary care settings with guideline-based treatments." Its referral figure lists eGFR under 30, a sustained fall of more than 20 percent, an ACR consistently over 700 mg/g, and CKD with blood pressure refractory to four or more drugs, so a stable G3b with low albuminuria does not itself trigger referral. Where the cause of CKD is uncertain, referral is listed regardless of stage.

Treatment that applies across this band. The SGLT2 inhibitor suggestion for people without diabetes or heavy albuminuria (Recommendation 3.7.3, 2B) covers eGFR 20 to 45, so it reaches G3b in full; the stronger recommendations for type 2 diabetes, an ACR of 200 mg/g or higher, or heart failure (3.7.1 and 3.7.2, 1A) apply down to an eGFR of 20. KDIGO reports a 37 percent reduction in the risk of kidney disease progression across 13 trials, irrespective of diabetes status. Once started, "it is reasonable to continue an SGLT2i even if the eGFR falls below 20," and the small early dip in eGFR "is generally not an indication to discontinue therapy." ACE inhibitor or ARB by albuminuria category, with creatinine and potassium checked within 2 to 4 weeks of starting; KDIGO says to continue unless creatinine rises more than 30 percent within 4 weeks. A statin or statin plus ezetimibe for adults 50 and older (3.15.1.1, 1A). The blood pressure target KDIGO suggests is a systolic under 120 on standardized office measurement, when tolerated, with less intensive targets for frailty or falls.

Dosing and daily life. KDIGO asks clinicians to consider GFR when dosing kidney-cleared drugs and to use a creatinine plus cystatin C estimate where a drug's margin is narrow. It suggests 0.8 g/kg of protein a day at G3 to G5 and warns against more than 1.3 g/kg in people at risk of progression, with higher targets considered for frail or sarcopenic older adults. Potassium-rich processed foods are limited when there is a history of high potassium. On sick-day rules, the guideline is honest: the advice to pause sulfonylureas, ACE inhibitors, diuretics, metformin, ARBs, NSAIDs and SGLT2 inhibitors during dehydrating illness is widely endorsed, but "there is a paucity of evidence to support sick day rules," and mistakes about when to restart can cause harm.