Metformin vs. Invokana

See how Metformin and Invokana compare on approved uses, dosing, side effects, and cost.

Key Takeaways

  • Metformin and Invokana both lower blood sugar in type 2 diabetes, but metformin works mainly in the liver and gut while Invokana works in the kidneys.

  • Metformin is usually prescribed first because of its long safety record and low cost, while Invokana is often added on or chosen for its heart and kidney benefits.

  • The two drugs cause different side effects: metformin mainly causes digestive upset, while Invokana raises the risk of genital and urinary infections.

Metformin vs. Invokana Drug Summary

Metformin

Metformin is a biguanide, the first-line oral medication for type 2 diabetes. It lowers blood sugar mainly by reducing how much glucose the liver releases and improving the body's response to insulin. It comes as a tablet or liquid, usually taken with meals once or twice a day, or once daily for the extended-release form.

Invokana

Invokana (canagliflozin) is an SGLT2 inhibitor used to control blood sugar in type 2 diabetes. It works by blocking glucose reabsorption in the kidneys, so extra sugar leaves the body through urine. It is taken as a single tablet once a day, before the first meal, and can also lower cardiovascular and kidney risks in certain patients.

Metformin vs. Invokana Side Effects

Metformin

Most common
Diarrhea (>5%)
Nausea/vomiting (>5%)
Flatulence (>5%)
Asthenia (>5%)

Invokana

Most common
Genital yeast infection (up to 11%)
Urinary tract infection (up to 6%)
Increased urination (up to 5%)
Male genital yeast infection (up to 4%)

Metformin vs. Invokana Dosage

Metformin

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 500 mg twice daily Week 1
Maximum dose 500 mg once daily Week 1
Dose changes 2 increases As tolerated

Invokana

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 100 mg once daily At the start
Maximum dose 100 mg once daily Same as starting
Dose changes None Fixed dose

Metformin vs. Invokana Indications

Metformin

Metformin is FDA-approved to improve blood sugar control in adults and children 10 and older with type 2 diabetes, usually alongside diet and exercise. Doctors also prescribe it off-label for polycystic ovary syndrome and for weight management in people with prediabetes.

  • Type 2 diabetes in adults (FDA-approved)

  • Type 2 diabetes in children 10+ (FDA-approved)

  • PCOS (off-label)

  • Prediabetes or weight management (off-label)

Invokana

Invokana is FDA-approved as an add-on to diet and exercise to control blood sugar in adults and children 10 and older with type 2 diabetes. It's also approved to lower cardiovascular risk in heart disease and to slow kidney disease in people with diabetic kidney disease.

  • Type 2 diabetes in adults (FDA-approved)

  • Type 2 diabetes in children 10+ (FDA-approved)

  • Lowering CV event risk in heart disease (FDA-approved)

  • Slowing diabetic kidney disease (FDA-approved)

Metformin vs. Invokana Pros and Cons

Metformin

Metformin has decades of safety data, a low risk of causing low blood sugar on its own, and is the guideline-recommended starting point for type 2 diabetes. It is inexpensive as a generic, though it does not carry FDA-approved cardiovascular or kidney protection claims.

Pros

  • Decades of real-world safety data as first-line therapy

  • Low risk of hypoglycemia when used alone

  • Typically $4 to $30 per month as a generic, before insurance

  • Simple oral dosing, no injections needed

Cons

  • Common GI side effects, especially when starting

  • Boxed warning for rare but serious lactic acidosis

  • Not usable in severe kidney impairment

  • No FDA-approved heart or kidney protection claim

Invokana

Invokana carries FDA-approved cardiovascular and kidney protection claims beyond blood sugar control, which metformin does not have. It is a once-daily tablet, but it raises the risk of genital yeast infections and carries its own boxed warning for lower limb amputation.

Pros

  • FDA-approved to reduce cardiovascular event risk

  • FDA-approved to slow diabetic kidney disease progression

  • Once-daily oral tablet

  • Can modestly reduce body weight and blood pressure

Cons

  • Boxed warning for increased leg and foot amputation risk

  • Raises risk of genital yeast infections and UTIs

  • Rare risk of euglycemic diabetic ketoacidosis

  • Roughly $550 to $830 per month without insurance, before savings programs

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