QUESTION: I am a 50-year-old man diagnosed with type 2 diabetes eight months ago. I take metformin 500 mg after lunch and Diamicron MR 30 mg after breakfast. My glucose is described as controlled, but I have mouth and throat ulcers, constipation, erectile difficulties, and have lost 11 kg. Are these medicine side effects, and what should I do?
Do not assume that all four problems are harmless medication effects. Metformin commonly causes diarrhea, nausea, and abdominal discomfort, while Diamicron MR (gliclazide) can cause low glucose and sometimes constipation. Neither medicine usually explains persistent mouth or throat ulcers, and an unplanned 11 kg loss over eight months needs prompt medical review even if glucose readings look good. Erectile dysfunction is common with diabetes but may also signal vascular disease, low testosterone, medication effects, or emotional stress.
Answer by Dr. Albana Greca, MD, MMedSc
Hi Husain,
Your symptoms should be assessed separately. Do not stop either medicine, begin antifungal treatment, or use stimulant laxatives before review.
Diabetes can increase dry mouth, gum disease, and oral thrush risk, especially when glucose is high. Thrush usually causes creamy white patches, redness, burning, or soreness; it should not be diagnosed from an ulcer alone.
Other causes include aphthous ulcers, dental disease, trauma, reflux, tobacco, iron or vitamin B12 deficiency, infection, inflammatory disease, or medicines. Arrange an examination if an ulcer persists beyond two weeks, recurs, affects swallowing, or occurs with fever, rash, or weight loss.
Review our metformin side-effects guide and diabetes medicine safety guide.
Metformin is generally weight neutral or may cause modest weight loss, but 11 kg should not automatically be celebrated. Whether it is appropriate depends on your starting weight, current BMI, waist size, diet, and whether the loss was intentional.
Unexplained loss may result from uncontrolled glucose, severe restriction, thyroid disease, infection, gastrointestinal disease, depression, cancer, or another illness. Ask for your actual HbA1c, glucose pattern, and weight trend. The BMI and waist-to-height calculator provides context but does not replace examination.
Constipation is reported with gliclazide, although metformin more commonly causes loose stools. It may also result from low fluid or fiber intake, restrictive dieting, reduced activity, thyroid disease, dehydration from high glucose, iron or calcium products, or other medicines.
Do not assume intestinal Candida is the cause; stool testing for yeast is not a routine constipation evaluation. Start with adequate fluids, vegetables, legumes, whole grains or other tolerated fiber, and regular activity. A clinician should review persistent constipation before regular senna use, especially if there is pain, vomiting, bleeding, anemia, or weight loss. See the balanced diabetes meal-plan guide.
Erectile difficulty may be related to blood-vessel disease, neuropathy, blood pressure, cholesterol, smoking, low testosterone, depression, relationship stress, or medicines. It is not proof of irreversible damage.
Because erectile dysfunction can be an early cardiovascular warning, ask for blood pressure, lipid, kidney, and cardiovascular-risk assessment. If low desire, fatigue, reduced shaving frequency, or other signs suggest hormone deficiency, a morning testosterone test may be appropriate. Read our diabetes and erectile-dysfunction guide.
Erection medicines may help, but they must not be combined with nitrate medicines for chest pain. Treatment requires review of the heart and medicine history.
Yes. Gliclazide is a sulfonylurea and can cause hypoglycemia, especially when meals are skipped, food intake has fallen, weight has been lost, exercise has increased, alcohol is used, or kidney function has changed. Symptoms may include hunger, sweating, shaking, dizziness, irritability, confusion, or weakness.
Check glucose during symptoms and record meals and treatment in a blood sugar log. Review sulfonylurea side effects. Repeated readings below 70 mg/dL require prompt dose review.
Seven years without children does not identify which partner has a fertility problem. Both partners should be assessed. Male evaluation commonly includes history, examination, and semen analysis, with hormone tests when indicated. A urologist or male-fertility specialist is appropriate rather than evaluating only the female partner.
Seek prompt care for continuing unexplained weight loss, inability to eat or swallow, an ulcer lasting longer than two weeks, black or bloody stool, persistent vomiting, severe abdominal pain, fever, swollen neck glands, or marked weakness. Call emergency services for unconsciousness, seizure, inability to swallow, chest pain, or severe breathing difficulty. Do not stop either diabetes medicine without medical instructions.
The old answer incorrectly attributed constipation to intestinal Candida and treated 11 kg of weight loss as automatically beneficial. The priority is prompt review. Ask for the actual glucose results and investigate the weight loss, persistent oral lesions, bowel change, sexual health, and fertility rather than assuming diabetes is the only cause.
Educational safety note: This answer is for general diabetes education only. It does not replace personal medical, dental, urological, or fertility care. Do not stop, double, or change metformin, Diamicron MR, laxatives, antifungals, supplements, diet, or exercise without speaking with your healthcare provider.
Last reviewed: July 2026.
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