Jardiance and metformin are both effective at lowering blood sugar in type 2 diabetes, but neither is universally “better.” Which one works best depends on your specific health profile, particularly whether you have heart disease, kidney disease, or heart failure. For straightforward blood sugar control in someone without those conditions, metformin remains the standard first-line treatment. But for people with cardiovascular or kidney complications, Jardiance has proven benefits that metformin simply hasn’t matched in clinical trials.
How Each Drug Works
Metformin and Jardiance lower blood sugar through completely different pathways, which is why they’re often used together rather than as either/or choices.
Metformin works primarily in the liver. It reduces the amount of glucose your liver produces and releases into your bloodstream, a process called gluconeogenesis. It also helps your body respond better to insulin. It’s been used for decades and has one of the longest safety track records of any diabetes medication.
Jardiance (empagliflozin) works in the kidneys. It blocks a transporter responsible for reabsorbing glucose from urine back into the blood. The result: your body flushes excess glucose out through urine instead of recycling it. This mechanism is entirely independent of insulin, which means it works regardless of how insulin-resistant you are.
Blood Sugar Lowering
Metformin has the stronger track record for pure blood sugar reduction. As a monotherapy, it typically lowers A1C by about 1.0 to 1.5 percentage points, depending on starting levels and dosage. Jardiance is more modest in comparison: clinical data shows the 10 mg dose reduces A1C by about 0.5%, with the 25 mg dose achieving roughly 0.6%.
If blood sugar control is your primary concern and you don’t have significant heart or kidney issues, metformin delivers more glucose-lowering power per dollar spent. That’s a major reason it has been the default starting medication for type 2 diabetes for so long.
Heart and Kidney Protection
This is where Jardiance pulls ahead for certain patients. In the EMPEROR-Reduced trial, empagliflozin reduced the combined risk of cardiovascular death or hospitalization for heart failure by 28% in people with diabetes. It cut the risk of heart failure hospitalization alone by about 35%. These benefits held up even in patients without diabetes, suggesting the heart-protective effects go beyond blood sugar control.
Jardiance also slows the progression of chronic kidney disease. For people with reduced kidney function and albumin in their urine, it helps preserve kidney function over time.
Metformin has not demonstrated these same cardiovascular or kidney-protective effects in large outcome trials. It’s a solid glucose-lowering drug, but it doesn’t carry the same evidence for preventing heart failure hospitalizations or protecting kidney function.
What Current Guidelines Recommend
The American Diabetes Association’s 2025 Standards of Care reflect a shift in thinking. Metformin is still described as a commonly used first-line medication when the only goal is lowering blood sugar. But for patients with specific conditions, SGLT2 inhibitors like Jardiance now take priority, regardless of A1C levels.
Specifically, the guidelines recommend Jardiance (or another SGLT2 inhibitor with proven benefits) for people with:
- Established or high-risk cardiovascular disease: to reduce cardiovascular events
- Heart failure (reduced or preserved ejection fraction): to prevent hospitalizations
- Chronic kidney disease (eGFR between 20 and 60): to slow progression and reduce cardiovascular events
For these groups, the guidelines say an SGLT2 inhibitor should be used “independent of A1C, with or without metformin.” In other words, Jardiance can be started first, and metformin becomes the add-on rather than the foundation.
Weight Loss Differences
Jardiance has a notable edge when it comes to weight. Because it causes your body to excrete glucose (and the calories that come with it) through urine, weight loss is a consistent side effect. In a 24-week clinical trial comparing the two drugs, participants taking empagliflozin 10 mg lost an average of 6.7 kg (about 15 pounds), while those on metformin 500 mg twice daily lost only 0.9 kg (about 2 pounds).
Metformin is generally considered weight-neutral to mildly weight-reducing. It won’t cause weight gain like some diabetes medications, but meaningful weight loss isn’t something most people experience on it. If weight management is a significant part of your treatment goals, Jardiance has a clear advantage.
Kidney Function Requirements
Both drugs have limits based on how well your kidneys work, measured by estimated glomerular filtration rate (eGFR).
Metformin can be used at full dose down to an eGFR of 45. Between 30 and 44, the dose needs to be reduced and it shouldn’t be newly started. Below 30, metformin should be stopped due to the risk of a dangerous buildup of lactic acid.
Jardiance has its own kidney thresholds, but they’re nuanced. For blood sugar lowering specifically, it loses effectiveness as kidney function declines and shouldn’t be started for glucose control below an eGFR of 45. However, for heart and kidney protection, it can be initiated at lower eGFR levels (down to around 20 in some cases). Below an eGFR of 15, it’s not recommended.
Side Effects
The side effect profiles are quite different. Metformin’s most common issues are gastrointestinal: nausea, diarrhea, stomach cramps, and bloating, especially when starting or increasing the dose. These usually improve over a few weeks. Extended-release formulations tend to be easier on the stomach.
Jardiance’s main side effects stem from its mechanism. Flushing sugar into your urine creates a favorable environment for yeast and bacteria, so genital yeast infections and urinary tract infections are more common. Increased urination and mild dehydration can also occur. There’s a rare but serious risk of diabetic ketoacidosis, even when blood sugar levels appear normal, and a small increased risk of a severe genital infection called Fournier’s gangrene.
Cost Comparison
The price gap between these two drugs is enormous. Without insurance, generic metformin costs roughly $11 to $23 for a 500-tablet supply. Jardiance runs about $298 for a 15-tablet supply at the 25 mg strength, putting it at nearly $20 per pill compared to pennies per pill for metformin.
Insurance and manufacturer coupons can reduce the Jardiance cost substantially, but even with coverage, copays are typically much higher than for metformin. For patients without heart disease, kidney disease, or heart failure, metformin’s effectiveness at a fraction of the price makes it hard to justify Jardiance as a first choice on cost alone.
When They Work Best Together
Because metformin and Jardiance lower blood sugar through entirely separate pathways, they complement each other well. Adding Jardiance to metformin provides additional A1C reduction on top of what metformin is already doing, plus the cardiovascular and kidney benefits that metformin doesn’t offer. A fixed-dose combination tablet containing both drugs is available for convenience.
For many people with type 2 diabetes, the question isn’t really which drug is better. It’s whether you need one or both, and which should come first. If you have heart disease, heart failure, or chronic kidney disease, starting with Jardiance (or adding it early) is supported by strong evidence. If you don’t have those conditions and cost or simplicity matters, metformin remains a proven, affordable starting point.