Insulin Vs. Metformin: Drug Comparison

Insulin is a vital hormone produced by the pancreas that regulates blood sugar levels by facilitating the uptake of glucose into cells for energy production. It is essential for individuals with type 1 diabetes, who cannot produce insulin naturally, and is also used in some cases of type 2 diabetes to help control blood glucose levels when other medications are insufficient. Insulin therapy involves the administration of synthetic or animal-derived insulin, through injections or insulin pumps, and requires careful monitoring to balance blood sugar levels and avoid low blood sugar. Side effects can include low blood sugar, weight gain, and, in some cases, allergic reactions at the injection site​.

Insulin has many different types and names. The information below is about brand name Humalog^®, which is a type of insulin lispro (a rapid-acting insulin).

Metformin is an oral medication commonly prescribed to manage blood sugar levels in individuals with type 2 diabetes. It works by decreasing glucose production in the liver, improving the body's sensitivity to insulin, and reducing the amount of sugar absorbed by the intestines. Metformin is often used as a first-line treatment due to its efficacy, safety profile, and additional benefits, such as weight stabilization and low risk of low blood sugar. Common side effects include gastrointestinal issues like nausea, diarrhea, and abdominal discomfort.

Rapid acting human insulin analog

Biguinide

Humalog (insulin lispro) is indicated:

• To improve glycemic control in adult and pediatric patients with diabetes mellitus

Metformin hydrochloride tablets are indicated:

• As an adjunct to diet and exercise to improve glycemic control in adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus

• See the Full Prescribing Information for important administration instructions

• Comes as an injection

• Typically taken orally once, twice, or three times daily

• Comes in 500 mg, 850 mg, and 1,000 mg tablets

Adverse reactions associated with Humalog include:

• Low blood sugar

• Allergic reactions

• Injection site reactions

• Abnormal distribution of fat

• Itch

• Rash

For metformin hydrochloride, the most common adverse reactions (>5%) are:

• Diarrhea

• Nausea/vomiting

• Flatulence

• Weakness

• Indigestion

• Abdominal discomfort

• Headache

• Do not use during episodes of low blood sugar

• Do not use in patients with hypersensitivity to insulin lispro or any of the excipients in Humalog

• Drug interactions: Drugs that may increase the risk of low blood sugar (antidiabetic agents, ACE inhibitors, angiotensin II receptor blocking agents, disopyramide, fibrates, fluoxetine, monoamine oxidase inhibitors, pentoxifylline, pramlintide, salicylates, somatostatin analog [e.g., octreotide], sulfonamide antibiotics), drugs that may decrease the blood glucose lowering effect (atypical antipsychotics, corticosteroids, danazol, diuretics, estrogens, glucagon, isoniazid, niacin, oral contraceptives, phenothiazines, progestogens [e.g., in oral contraceptives], protease inhibitors, somatropin, sympathomimetic agents [e.g., albuterol, epinephrine, terbutaline], thyroid hormones), drugs that may increase or decrease the blood glucose lowering effect (alcohol, beta-blockers, clonidine, lithium salts, pentamidine), drugs that may blunt the signs and symptoms of low blood sugar (beta-blockers, clonidine, guanethidine, reserpine)

• Severe renal impairment (eGFR below 30 mL/min/1.73 m²)

• Hypersensitivity to metformin

• Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma

• Drug interactions: Carbonic anhydrase inhibitors, drugs that reduce metformin clearance (such as ranolazine, vandetanib, dolutegravir, and cimetidine), alcohol

• Never share a Humalog prefilled pen, cartridge, reusable pen compatible with Lilly 3 mL cartridges, or syringe between patients, even if the needle is changed

• High blood sugar or low blood sugar with changes in insulin regimen

• Low blood sugar: May be life-threatening

• Low blood sugar due to medication errors

• Hypersensitivity reactions: May be life-threatening

• Hypokalemia: May be life-threatening

• Fluid retention and heart failure with concomitant use of thiazolidinediones (TZDs)

• High blood sugar and ketoacidosis due to insulin pump device malfunction

• Lactic acidosis: See Boxed Warning

• Vitamin B12 deficiency: Metformin may lower vitamin B12 levels

• Low blood sugar with concomitant use with insulin and insulin secretagogues

• Females and males of reproductive potential: Potential for an unintended pregnancy

WARNING: LACTIC ACIDOSIS

Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Symptoms included malaise, myalgias, respiratory distress, somnolence, and abdominal pain. Laboratory abnormalities included elevated blood lactate levels, anion gap acidosis, increased lactate/pyruvate ratio; and metformin plasma levels generally >5 mcg/mL.

Risk factors include renal impairment, concomitant use of certain drugs, age >65 years old, radiological studies with contrast, surgery and other procedures, hypoxic states, excessive alcohol intake, and hepatic impairment. Steps to reduce the risk of and manage metformin-associated lactic acidosis in these high risk groups are provided in the Full Prescribing Information.

If lactic acidosis is suspected, discontinue metformin hydrochloride tablets and institute general supportive measures in a hospital setting. Prompt hemodialysis is recommended.

*This information is from the label for brand name Humalog^®, which is a type of insulin lispro (a rapid-acting insulin). See the Full Prescribing Information for more complete information. Insulin has many different types and names, and this information may not be accurate for all medications that include insulin.

*This information is from the metformin hydrochloride label used by Epic Pharma, LLC. See the Full Prescribing Information for more complete information. Metformin may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient metformin.