CHAPTER PART 6 OF 9
What a dietician needs to understand about the glycaemic and pharmacological side, because it changes meal timing, carbohydrate distribution and how you read the file.
What a dietician needs to understand about the glycaemic and pharmacological side, because it changes meal timing, carbohydrate distribution and how you read the file.
KDIGO's recommendation is an individualised HbA1c between under 6.5 and under 8.0 percent, and it applies only to CKD not on dialysis. No guideline body sets an HbA1c target for dialysis patients at all. Aim toward the lower end where life expectancy is long, comorbidity low and the drugs do not cause hypoglycaemia. Aim toward 7.5 to 8.0 with high comorbidity, hypoglycaemia unawareness, macrovascular disease or CKD G4 to G5.
| Mechanism | Direction of error |
|---|---|
| Shortened red cell survival from uraemia and the dialysis circuit | Falsely low |
| Erythropoiesis-stimulating agents, reticulocytosis | Falsely low |
| Iron replacement therapy | Falsely low |
| Blood transfusion | Falsely low |
| Untreated iron deficiency, older red cell population | Falsely high |
| Carbamylation of haemoglobin from high urea, and metabolic acidosis | Falsely high |
Net effect: HbA1c consistently underestimates true glucose in advanced CKD. A cohort of haemodialysis patients with apparently normal HbA1c, described as "burnt-out diabetes", was spending 4.1 hours a day above 180 mg/dL on continuous glucose monitoring. Glycated albumin and fructosamine are not the answer either: the KDIGO 2026 draft states they offer no advantage over HbA1c and are biased by the hypoalbuminaemia these patients have.
Where continuous glucose monitoring is available, note that no body has issued CKD-specific time-in-range targets. The borrowed high-risk tier is: time in range above 50 percent (not the usual 70), time below 70 mg/dL under 1 percent, and time above 250 mg/dL under 10 percent. Real dialysis cohorts sit at 30 to 50 percent time in range.
The kidney contributes up to 20 to 25 percent of glucose production during a prolonged fast, and clears roughly 80 percent of injected insulin. Lose renal mass and you lose both the counter-regulation and the insulin clearance. In CKD, hypoglycaemia rates roughly double in people with diabetes. Insulin requirement falls by around 40 percent in type 1 and 50 percent in type 2 between early CKD and end-stage disease.
In a CGM study of 98 haemodialysis patients, 21 percent had dialysis-related hypoglycaemia, 14 percent during the session and 20 percent afterwards, and every single episode was asymptomatic. Mean sensor nadir was 61 mg/dL during dialysis and 58 mg/dL after. Half the patients had a nadir below the dialysate glucose concentration, and this happened at every dialysate glucose in use. Basal insulin requirement after a session runs about 25 percent lower, and the lowest glucose tends to fall around 12 hours after a session.
Practical consequence: never rely on symptoms. Ensure the post-dialysis meal is eaten even when the patient is tired or nauseated. Do not let a dialysis day become a long fast.
Treat hypoglycaemia with 15 to 20 g of glucose tablets or gel, not fruit juice. A 240 ml glass of orange juice carries about 470 mg of potassium.
| Class | Kidney threshold | Dietetic consequence |
|---|---|---|
| Metformin | Continue to eGFR 30, halve dose at 30 to 44, stop below 30. ADA advises not to initiate below 45. | GI intolerance cuts intake. Check B12 after four years, and do not assume anaemia is renal. |
| SGLT2 inhibitors | Start at eGFR 20 or above, reasonable to continue below 20, stop on dialysis. | Carbohydrate must not be cut hard. Ketogenic or very low carbohydrate eating, defined as 20 to 50 g a day, plus prolonged fasting or illness, is the euglycaemic ketoacidosis recipe. Counsel on volume depletion and genital hygiene. Note these drugs lower severe hyperkalaemia risk. Below eGFR 45 they barely move glucose at all, so do not promise the patient a better sugar. |
| GLP-1 receptor agonists | No eGFR threshold for semaglutide, liraglutide or dulaglutide. FLOW showed a 24 percent reduction in the kidney composite. | The most important item on this page. Nausea, early satiety and vomiting cut energy and protein intake exactly when reserve is lowest. 15 to 40 percent of weight lost is lean mass, and there is no CKD-specific body composition data at all. Protect protein at the upper end of the permitted range, prioritise quality, add resistance exercise, and screen for wasting more often than twice a year. |
| Sulfonylureas | Avoid glibenclamide entirely. Glipizide is the preferred agent. Reconsider glimepiride below eGFR 15. | They fix meal timing: the patient must eat when they dose. This is the single biggest constraint on flexible meal patterns and on fasting. |
| DPP-4 inhibitors | Linagliptin needs no adjustment and is the practical choice in advanced CKD. | Weight neutral, low hypoglycaemia risk. Do not combine with a GLP-1 agonist. |
| Pioglitazone | No renal adjustment needed. | Fluid retention, 2 to 4 kg weight gain, oedema and fracture risk. Poorly matched to a fluid-restricted patient. |
| Insulin | No threshold, but requirement falls steadily. | Carbohydrate counting stays valid, but ratios must be re-derived as eGFR falls. Post-dialysis basal need about 25 percent lower. |
| Finerenone | eGFR 25 or above, normal potassium, on maximum tolerated RAS blockade. Do not start if K is above 5.0. | Dietary potassium is what keeps the patient on this drug (2A in KDIGO 2022, upgraded to 1A in the unratified 2026 draft). Withhold above 5.5, restart at 10 mg when below 5.0. A dietician who brings K from 5.4 to 4.9 has done something a prescription could not. |
| Potassium binders | Patiromer exchanges calcium. Sodium zirconium cyclosilicate exchanges sodium. | SZC delivers about 800 mg of sodium at a 10 g dose, roughly 40 percent of the sodium allowance, and causes oedema dose-dependently. Patiromer adds a calcium load and depletes magnesium. Separate from other oral drugs by 2 to 3 hours. |
| Sodium bicarbonate | KDIGO 2024 now treats only below a serum bicarbonate of 18 mmol/L, down from 22. | 177 mg sodium per 650 mg tablet. Three a day is 530 mg. Subtract it from the diet prescription or you will chase oedema you prescribed. |
| Oral iron | Any stage | Absorption is crushed by tea and coffee polyphenols, calcium-based binders and phytate, all abundant in a Deccan diet. Separate from binders and calcium, and consider alternate-day dosing. |
Any dehydrating illness: vomiting, diarrhoea, fever, sweats, reduced intake, unusual drowsiness, urinary infection.
SGLT2 inhibitor, metformin, ACE inhibitor or ARB, diuretics (check first if for heart failure), NSAIDs, sulfonylureas, finerenone. Pause 1 to 3 days.
Insulin. Keep at least a low dose in an insulin-requiring patient. Stopping basal insulin during illness is a classic and dangerous error.
Only after eating normally for 24 hours and no longer acutely unwell. Check blood ketones before restarting an SGLT2 inhibitor, and act above 0.6 mmol/L.
Ketoacidosis red flags to teach the family: nausea, vomiting, abdominal pain, deep or laboured breathing, drowsiness. Stop the SGLT2 inhibitor and seek urgent care even if the glucose reading is normal.
Intentional weight loss is recommended in obesity with CKD, and the guideline attaches that specifically to eGFR 30 or above. Below that threshold the guidance goes quiet, because energy restriction collides with protein-energy wasting. In prevalent dialysis patients, higher BMI is consistently associated with lower mortality, and the survival advantage tracks muscle mass surrogates at least as strongly as fat. That is not a licence to encourage weight gain, but weight loss is not a routine goal on dialysis. The recognised exception, now written into the KDIGO 2026 draft, is weight loss to achieve transplant listing.