To investigate the effects of using a high monounsaturated fatty acid (MUFA) and low carbohydrate formula on blood glucose levels and diarrhea treatment effects in critically ill neurological patients. A self-controlled before-and-after study design was employed, with 13 patients admitted to the neurology intensive care unit (ICU) of the First Affiliated Hospital of Sun Yat-sen University from November to December 2023, who were treated with a high MUFA and low carbohydrate formula [Glucerna enteral nutrition (EN) preparation]. Changes in blood glucose parameters within 7 days before and after the use of Glucerna EN preparation were analyzed, including standard deviation (SD) of blood glucose, mean blood glucose (MG), median blood glucose, mean amplitude of glycemic excursions (MAGE), largest amplitude of glycemic excursions (LAGE), coefficient of variation (CV) of blood glucose, the incidence of hyperglycemia (> 7.8 mmol/L) and severe hyperglycemia (> 13.9 mmol/L), and daily insulin dose. Changes in total protein (TP), albumin (ALB), hemoglobin (Hb), C-reactive protein (CRP), and white blood cell count (WBC) were observed before and after intervention. Improvement in diarrhea symptoms, Hart diarrhea score, Bristol Stool classification score, and incontinence dermatitis classification were also analyzed before and after the use of Glucerna EN preparation. A total of 13 critically ill neurological patients were enrolled, among whom 9 patients had a history of hyperglycemia and 8 patients had diarrhea symptoms. After intervention with Glucerna, the patients' SD of blood glucose, MG, median blood glucose, MAGE, LAGE, CV of blood glucose, incidence of hyperglycemia, incidence of severe hyperglycemia, and daily insulin dose were all lower than those before the intervention [SD of blood glucose (mmol/L): 1.83±1.11 vs. 2.10±1.13, MG (mmol/L): 8.87±2.03 vs. 9.75±1.37, median blood glucose (mmol/L): 9.12±1.67 vs. 10.17±0.48, MAGE (mmol/L): 0.66±0.31 vs. 0.78±0.32, LAGE (mmol/L): 4.95±3.64 vs. 5.58±3.10, CV of blood glucose: 16.00% (11.00%, 28.50%) vs. 18.00% (12.50%, 27.50%), hyperglycemia incidence: 47.31% vs. 74.66%, severe hyperglycemia incidence: 6.08% vs. 6.71%, daily insulin dose (U): 5.25 (0.00, 32.59) vs. 20.76 (0.00, 66.88)], with a significant decrease in daily insulin dose after the intervention (P < 0.05); TP, ALB, Hb, CRP and WBC showed no significant changes before and after the intervention with Glucerna EN preparation. The improvement time of diarrhea symptoms after intervention was (3.50±1.41) days, and the Hart diarrhea score on the seventh day after intervention (4.88±3.48 vs. 10.00±3.38) and the Bristol Stool classification score on the third and seventh days after intervention (5.87±0.35, 5.50±0.53 vs. 6.50±0.53) were significantly lower than before the intervention (all P < 0.05). Before the intervention with Glucerna EN preparation, the classification of incontinence dermatitis was mainly classified as Grade 2 severity (71.43%); after the intervention, it significantly improved by the seventh day, with Grade 1 being the main classification (57.14%). The high MUFA and low carbohydrate formula has a positive effect on blood glucose control and diarrhea treatment in critically ill neurological patients.