Irritable Bowel Syndrome (IBS): Given the patient's age, history of diabetes with good control (A1C 5.0%), and presentation of non-bloody diarrhea with urgency without abdominal pain, fever, or recent travel, IBS is a plausible diagnosis. The absence of alarm symptoms such as blood in stool, significant weight loss, or fever makes IBS a reasonable consideration.

Infectious Gastroenteritis: Although the patient reports no travel, infectious gastroenteritis can occur through contaminated food or water locally. The lack of fever and blood in the stool makes bacterial causes less likely, but viral gastroenteritis is still a possibility.
Medication-Induced Diarrhea: Given the patient's history of diabetes, they may be on medications that could contribute to diarrhea, such as metformin. A review of their current medications is warranted.
Lactose Intolerance or Other Food Intolerances: These conditions can cause chronic diarrhea, especially if the patient has recently increased their intake of lactose-containing products or other potentially irritating foods.

Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can present with chronic diarrhea and urgency. Although less likely given the absence of blood and abdominal pain, missing IBD could lead to significant morbidity.
Colorectal Cancer: Although rare in the context of this presentation, new-onset diarrhea in an older adult could be a symptom of colorectal cancer, especially if there's an unexplained iron deficiency anemia or significant weight loss.
Ischemic Colitis: This condition can present with sudden onset of diarrhea, often with abdominal pain, but pain may be absent in some cases. Given the patient's age and history of diabetes (which can affect vascular health), ischemic colitis is a critical diagnosis not to miss.

Microscopic Colitis: This condition is characterized by chronic, watery diarrhea without blood, which fits the patient's presentation. It's more common in older adults but is less common than IBS or infectious causes.
Bile Acid Diarrhea: This can occur due to various reasons, including post-cholecystectomy or bile acid malabsorption. It's a rare cause of chronic diarrhea but should be considered if common causes are ruled out.
Hormone-Producing Tumors (e.g., VIPoma): These are rare tumors that can cause severe, chronic diarrhea due to the excessive production of certain hormones. They are unlikely but would be critical to diagnose due to their potential impact on the patient's quality of life and prognosis.