Metformin vs. Insulin

Metformin lowers blood glucose by influencing insulin sensitivity. It is used for treating type 2 diabetes and increases sensitivity to insulin in various tissues, lowering blood sugar levels.

• Metformin does not increase insulin concentration or cause low blood glucose levels.
• It can reduce complications of diabetes such as heart disease, blindness, and kidney disease. Metformin is also used for treating polycystic ovaries and weight gain caused by psychoses medications.

Insulin is a naturally-occurring hormone used by the body’s cells to remove and use glucose from the blood. In diabetes, there is a reduced ability to use glucose, resulting in elevated blood sugar levels.

• Insulin prevents or reduces long-term complications of diabetes by increasing glucose uptake by cells and reducing blood glucose concentration.
• It is administered through subcutaneous injections.

QUESTION

What are the side effects of metformin and insulin?

Metformin side effects

The most common side effects of metformin are:

• Weakness or lack of energy
• Respiratory tract infections
• Low levels of vitamin B-12
• Low blood glucose
• Constipation
• Indigestion
• Muscle pain
• Heartburn
• Chills

A serious but rare side effect is lactic acidosis, which can be fatal. Symptoms include weakness, trouble breathing, abnormal heartbeats, unusual muscle pain, stomach discomfort, light-headedness, and feeling cold. Patients at risk include those with kidney or liver function impairment, congestive heart failure, severe acute illnesses, and dehydration.

Insulin side effects

The most common side effect of insulin therapy is hypoglycemia, which can cause confusion, nausea, hunger, tiredness, perspiration, headache, heart palpitations, numbness around the mouth, tingling in the fingers, tremors, muscle weakness, blurred vision, cold temperature, excessive yawning, irritability, and loss of consciousness. Patients may experience blurred vision when transitioning from elevated to normal blood sugar levels.

Other side effects include headaches, skin reactions at the injection site, worsening of diabetic retinopathy, changes in body fat distribution, allergic reactions, sodium retention, general body swelling, weight gain, and reduced potassium blood levels.

What is the dosage of metformin vs. insulin?

Metformin dosage

• For treating type 2 diabetes in adults, metformin is usually started at a dose of 500 mg twice a day or 850 mg once daily. The dose is gradually increased as tolerated and based on glucose levels. The maximum daily dose is 2550 mg in three divided doses.
• If using extended release tablets, the starting dose is 500 mg or 1000 mg daily with the evening meal. The dose can be increased by 500 mg weekly up to a maximum dose of 2000 mg, except for Fortamet (2500 mg once daily or in two divided doses). Glumetza tablets (500-1000 mg) are given once daily. Metformin should be taken with meals.
• For pediatric patients aged 10-16 years, the starting dose is 500 mg twice a day. The maximum dose is 2000 mg in divided doses.
• Children older than 17 years may receive 500 mg of extended release tablets daily, up to a maximum dose of 2000 mg. Extended release tablets are not approved for children younger than 17 years.
• Metformin can be used in patients with mild to moderate renal impairment but should not be used in patients with an estimated glomerular filtration rate (eGFR) below 30 mL/minute/1.73 m2. Starting metformin in patients with an eGFR between 30-45 mL/minute/1.73 m2 is not recommended. Metformin should be stopped before administering iodinated contrast and kidney function should be evaluated.

Insulin dosage

The abdomen is the preferred injection site for insulin. Injection sites must be rotated to prevent lipodystrophy. Dosing is adjusted for each patient, and a combination of short-acting/rapid-acting and intermediate or long-acting insulin is typically used.

What drugs interact with metformin and insulin?

Metformin drug interactions

• Cimetidine (Tagamet) can increase metformin levels in the blood by 40%, causing more side effects.
• Contrast media can reduce kidney function and increase metformin concentrations. Metformin should be stopped before and after contrast media use.
• Thiazide diuretics, steroids, estrogens, and oral contraceptives can increase blood glucose levels and reduce metformin’s effectiveness.
• Alcohol consumption increases the risk of lactic acidosis.

Insulin drug interactions

Various substances can affect glucose metabolism and require insulin dose adjustment and close monitoring.

Examples of substances that may reduce insulin’s blood glucose-lowering effect include:

• Corticosteroids
• Danazol
• Diazoxide
• Diuretics
• Sympathomimetic agents (e.g., epinephrine, albuterol, terbutaline)
• Glucagon
• Isoniazid
• Phenothiazine derivatives
• Somatropin
• Thyroid hormones
• Estrogens
• Progestogens (e.g., in oral contraceptives)
• Protease inhibitors
• Atypical antipsychotic medications (e.g., olanzapine and clozapine)

Examples of substances that may increase insulin’s blood glucose-lowering effect include:

• Oral antidiabetic products
• ACE inhibitors
• Disopyramide
• Fibrates
• Fluoxetine
• MAO inhibitors
• Pentoxifylline
• Propoxyphene
• Salicylates
• Sulfonamide antibiotics

Beta-blockers, clonidine, lithium salts, and alcohol can either increase or reduce insulin’s blood glucose-lowering effect. Pentamidine may cause hypoglycemia followed by hyperglycemia. Sympatholytic medicinal products can reduce the signs and symptoms of hypoglycemia. Inhalable insulin may be affected by bronchodilators and other inhaled products.

Are metformin and insulin safe during pregnancy or breastfeeding?

Metformin

• There are no adequate studies in pregnant women, and insulin is usually considered the best treatment for pregnant women with diabetes.
• Metformin is excreted into breast milk and should not be used by nursing mothers.

Insulin

• Insulin is the preferred drug for controlling diabetes during pregnancy, and it is considered safe to use by nursing mothers.

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Summary

Metformin and insulin are medications used to treat diabetes. Metformin is used for type 2 diabetes and can also treat polycystic ovaries and weight gain caused by psychoses medications. Insulin is used for both type 1 and type 2 diabetes. Both medications have side effects and drug interactions that should be considered.