by Katie
(Texas)
QUESTION: My grandfather has diabetes and takes metformin and a product called Glucontrol. Over several years he has become quick to anger, says inappropriate things, and seems mentally different. Could diabetes or his medicines cause these personality changes, and how can the family help?
Progressive personality or behavior changes in an older adult require a medical assessment and should not be blamed automatically on diabetes, medication, or normal aging. Low or very high glucose can cause temporary confusion, irritability, or unusual behavior. Dementia, depression, infection, stroke, thyroid disease, vitamin B12 deficiency, medication effects, alcohol, sleep problems, and hearing or vision loss are also possible. Arrange a prompt appointment and seek emergency help for sudden confusion, stroke symptoms, severe low glucose, threats, or unsafe behavior.
Answer by Dr. Albana Greca, MD, MMedSc
Hi Katie,
The change you describe deserves compassion, but it also deserves a proper evaluation. Becoming disinhibited, unusually angry, crude, forgetful, suspicious, or unable to manage familiar tasks may occur with cognitive impairment or another medical problem. Dementia is not a normal or inevitable part of aging.
Yes, temporarily. Hypoglycemia can cause irritability, confusion, sweating, shaking, weakness, sleepiness, poor coordination, or behavior that seems out of character. Older adults may show fewer typical warning symptoms.
If “Glucontrol” is actually Glucotrol or glipizide, it is a sulfonylurea and can cause prolonged low glucose, especially when meals are missed or kidney function is reduced. Confirm the exact name and ingredients from the bottle rather than assuming what the product contains.
When unusual behavior occurs, check his glucose if it can be done safely. If it is below 70 mg/dL and he is awake and able to swallow, follow his prescribed low-glucose plan. If he is unconscious, having a seizure, or cannot swallow safely, call 911 and use glucagon if available and someone knows how.
Very high glucose can cause dehydration, weakness, drowsiness, confusion, and a hyperglycemic crisis, particularly in older adults. However, glucose swings do not explain every gradual personality change. A normal reading during an episode also does not rule out dementia, depression, medication effects, or another illness.
Use a blood sugar log to record the behavior, glucose, meals, medicines, sleep, and symptoms at the same time.
Metformin is not generally considered a direct cause of progressive anger, disinhibition, or dementia. Long-term use can lower vitamin B12, however, and B12 deficiency may contribute to anemia, nerve symptoms, fatigue, or cognitive problems. His clinician should consider checking B12, particularly after several years of treatment or if anemia or neuropathy is present.
Do not stop metformin or another medicine without medical advice. Abruptly changing diabetes treatment may cause severe hyperglycemia.
A gradual decline over months or years may be related to mild cognitive impairment, Alzheimer disease, vascular dementia, another neurologic disorder, depression, alcohol use, poor sleep, or hearing and vision loss. A sudden change over hours or days is more suggestive of delirium, which may be caused by infection, dehydration, medication toxicity, electrolyte problems, kidney or liver failure, pain, or another acute illness.
There is no basis for automatically ordering pancreatic, colon, or liver cancer tests solely because his personality changed. Cancer screening and diagnostic tests should follow his symptoms, examination, age, health, and routine screening history.
Bring written examples of what changed, when it began, and whether it is worsening. Mention missed medicines, repeated questions, getting lost, falls, hallucinations, poor hygiene, unsafe driving, or difficulty handling money.
Choose a calm moment rather than confronting him during an angry episode. Speak slowly, use short sentences, and offer one choice or task at a time. Avoid arguing about every incorrect or inappropriate statement when no immediate danger exists.
Compassion does not require accepting abuse. A calm boundary may be: “I want to help, but I will step away while you are shouting.” Involve another trusted adult, and ask his clinician how the family can participate in the evaluation. Our page on diabetes, personality, and mood changes provides additional context.
Call 911 for sudden confusion, face drooping, one-sided weakness, trouble speaking, a seizure, loss of consciousness, severe breathing difficulty, or glucose that remains dangerously low despite treatment. If he threatens violence, has a weapon, wanders into danger, or cannot be kept safe, move to a safe place and contact emergency services.
The pattern described is not enough to identify one cause. Confirm whether “Glucontrol” is glipizide or a supplement, check glucose during episodes, and arrange a comprehensive geriatric and medication review. Progressive behavior change deserves cognitive assessment; sudden change should be treated as a possible medical emergency.
Educational safety note: This answer is for general diabetes education only. It does not replace personal medical, neurologic, or mental-health evaluation. Do not start, stop, or change metformin, glipizide, supplements, or other medicines without speaking with his healthcare provider.
Last reviewed: July 2026.
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