Metformin is employed alongside a balanced diet and exercise regimen, and sometimes in combination with other medications, to manage elevated blood sugar levels. It is primarily utilized in patients diagnosed with type 2 diabetes. The regulation of high blood sugar aids in averting complications such as kidney damage, vision impairment, nerve disorders, limb amputation, and sexual function impairments. Effective management of diabetes can also lower the risk of experiencing a heart attack or stroke.

The mechanism of action of metformin involves facilitating the restoration of your body’s natural response to insulin. Additionally, it reduces the production of sugar by your liver and the absorption of sugar by your stomach and intestines.


Levothyroxine is utilized for the treatment of hypothyroidism, a condition characterized by an underactive thyroid gland. It serves to substitute or supplement the thyroid hormone that is typically generated by the thyroid gland. Decreased levels of thyroid hormone may arise naturally or due to radiation/medications-induced damage to the thyroid gland or its surgical removal. Adequate thyroid hormone levels are crucial for sustaining regular mental and physical functions. In children, ensuring an adequate supply of thyroid hormone is essential for their normal mental and physical growth. Additionally, this medication is employed in the management of various other thyroid disorders such as thyroid cancer. However, it is not recommended for addressing infertility unless the cause is specifically attributed to low levels of thyroid hormone.

How to use levothyroxine

Before starting to take levothyroxine, it’s essential to read the Patient Information Leaflet provided by your pharmacist. This should be done each time you refill your prescription. If you have any questions, don’t hesitate to ask your doctor or pharmacist for clarification.

Follow your doctor’s instructions and take this medication orally as directed, usually once daily on an empty stomach, 30 minutes to 1 hour before breakfast. Use a full glass of water unless advised otherwise by your doctor.

If you are prescribed the capsule form of this medication, swallow it whole without splitting, crushing, or chewing. Individuals who cannot swallow capsules whole, such as infants or small children, should use the tablet form of the medication.

For infants or children who cannot swallow tablets whole, crush the tablet and mix it with 1 to 2 teaspoons (5 to 10 milliliters) of water. Administer the mixture using a spoon or dropper immediately. Do not prepare this mixture in advance or mix the tablet with soy infant formula. Consult your pharmacist for detailed instructions.

The dosage of levothyroxine is determined based on factors such as your age, weight, medical condition, laboratory test results, response to treatment, and other medications you may be taking. Inform your doctor and pharmacist about all the products you use, including prescription drugs, over-the-counter drugs, and herbal products.

Take this medication regularly to derive the most benefit from it, and try to take it at the same time each day to help remember. Do not discontinue this medication without consulting your doctor first, as thyroid replacement therapy is typically a lifelong treatment.

There are various brands of levothyroxine available. Do not switch brands unless advised by your doctor or pharmacist.

Certain medications, such as cholestyramine, colestipol, colesevelam, antacids, sucralfate, simethicone, iron supplements, sodium polystyrene sulfonate, calcium supplements, orlistat, sucroferric oxyhydroxide, lanthanum, sevelamer, and others, can decrease the absorption of thyroid hormone in your body. If you are taking any of these medications, take them at least 4 hours apart from levothyroxine.

Symptoms of low thyroid hormone levels include fatigue, muscle pains, constipation, dry skin, weight gain, slow heart rate, or sensitivity to cold. Inform your doctor if your condition worsens or persists after several weeks of taking this medication.

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Pros and Cons of metformin and levothyroxine



  • Effective in lowering blood sugar levels
  • Weight management
  • Cardiovascular benefits
  • Low risk of hypoglycemia


  • Gastrointestinal side effects
  • Lactic acidosis risk
  • Vitamin B12 deficiency
  • Not suitable for everyone



  • Effective in treating hypothyroidism
  • Well-tolerated
  • Improves quality of life
  • Long-term use


  • Requires consistent dosing
  • Potential for over-treatment
  • Interactions with other medications
  • Monitoring required

Differences Between metformin and levothyroxine


It is primarily used to manage high blood sugar levels in patients with type 2 diabetes.


This medication is used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone.

Alternative to metformin and levothyroxine

Alternative to Metformin

Sulfonylureas (e.g., glipizide, glyburide):

Stimulate insulin release from the pancreas to lower blood sugar levels.

Alternative to Levothyroxine (for hypothyroidism):

Natural desiccated thyroid (NDT) hormones (e.g., Armour Thyroid, Nature-Throid):

Contain both T4 and T3 hormones derived from animal thyroid glands.

Interactions between your drugs

levothyroxine metformin

Monitoring is crucial when using certain medications that may affect the effectiveness of insulin and other antidiabetic agents. These drugs include atypical antipsychotics, corticosteroids, diuretics, estrogens, gonadotropin-releasing hormone agonists, human growth hormone, phenothiazines, progestins, protease inhibitors, sympathomimetic amines, thyroid hormones, L-asparaginase, alpelisib, copanlisib, danazol, diazoxide, isoniazid, megestrol, omacetaxine, phenytoin, sirolimus, tagraxofusp, temsirolimus, as well as pharmacologic doses of nicotinic acid and adrenocorticotropic agents. These medications can lead to hyperglycemia, glucose intolerance, new-onset diabetes mellitus, or exacerbation of existing diabetes, affecting blood glucose control.

Management strategies include caution when prescribing drugs that can impact glucose metabolism in diabetic patients. Close monitoring of blood glucose levels is recommended after starting or stopping these medications, with adjustments made to the dosages of concurrent antidiabetic agents as needed. Patients should be educated to inform their doctor if they consistently have high blood glucose levels or experience symptoms such as excessive thirst and increased urination frequency. Additionally, patients should be watched for signs of hypoglycemia when these drugs are removed from their treatment plan.

Drug and food interactions

metformin food

AVOID ALCOHOL INTERACTION: Alcohol can intensify metformin’s impact on lactate metabolism, increasing the risk of lactic acidosis. It may also lead to hypoglycemia or hyperglycemia in diabetic patients. While hypoglycemia is rare with metformin alone, alcohol consumption can elevate this risk, particularly when taken on an empty stomach or after exercise. This occurs due to alcohol’s inhibition of gluconeogenesis and the body’s response to low blood sugar. Hypoglycemic episodes can persist for 8 to 12 hours post-alcohol ingestion. Chronic alcohol abuse can further lead to impaired glucose tolerance and hyperglycemia. However, moderate alcohol intake typically doesn’t affect blood glucose levels in well-controlled diabetic patients.

FOOD INTERACTION: Food can impact the absorption of metformin differently based on whether it’s an immediate-release or extended-release formulation. Taking immediate-release metformin with food decreases peak plasma concentration (Cmax) and systemic exposure (AUC) by 40% and 25%, respectively, and delays time to peak plasma concentration (Tmax) by 35 minutes compared to fasting administration. On the other hand, taking extended-release metformin with food increases AUC by 50% without affecting Cmax or Tmax, regardless of meal fat content. However, these findings may not apply to metformin formulations combined with other oral antidiabetic agents.

MANAGEMENT: It’s recommended to take metformin with meals and avoid excessive alcohol consumption during treatment. Diabetic patients should generally refrain from alcohol if their blood glucose is poorly controlled or if they have conditions like hypertriglyceridemia, neuropathy, or pancreatitis. Alcohol should not be consumed on an empty stomach or after exercise to minimize the risk of hypoglycemia. Patients should promptly notify their doctor if they experience potential signs of lactic acidosis such as fatigue, muscle pain, breathing difficulties, increased drowsiness, or abdominal discomfort, especially after stabilizing metformin therapy. Severe acidosis symptoms may include hypothermia, low blood pressure, and abnormal heart rhythms. If lactic acidosis is suspected, metformin should be discontinued immediately, and diagnostic tests such as electrolyte levels, ketones, blood glucose, blood pH, lactate levels, and metformin levels should be conducted. Lactic acidosis should be considered in diabetic patients with metabolic acidosis but no evidence of ketoacidosis.

levothyroxine food

ADJUST DOSING TIMING: The absorption of T4 thyroid hormone (levothyroxine) can be influenced by certain foods and the timing of meals relative to dosing. Fasting enhances T4 absorption, while foods such as soybean flour (found in infant formula), cottonseed meal, walnuts, dietary fiber, calcium, and calcium-fortified juices can reduce T4 absorption.

MANAGEMENT: It’s essential to administer T4 thyroid hormone preparations consistently regarding the time of day and their relation to meals to avoid significant fluctuations in serum levels. Foods that may impact T4 absorption should ideally be avoided within a few hours before or after dosing. For patients on continuous enteral nutrition for over a week, experts suggest interrupting tube feeding for at least 1 hour before and after administering levothyroxine and monitoring their thyroid function closely.


The interaction between metformin and levothyroxine primarily revolves around potential alterations in the absorption and effectiveness of these medications when taken concurrently. Metformin, commonly used to manage high blood sugar in type 2 diabetes, may impact the absorption of levothyroxine, a medication used to treat hypothyroidism. Factors such as timing of administration, food intake, and other medications can influence the interaction between metformin and levothyroxine. Therefore, it is crucial for healthcare providers to carefully monitor patients who are prescribed both metformin and levothyroxine, adjust dosages if necessary, and educate patients about potential interactions to ensure optimal treatment outcomes and patient safety.

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The information presented on this website is not intended as specific medical advice and is not a substitute for professional treatment or diagnosis. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.


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