Janumet is a fixed-dose combination tablet pairing sitagliptin (a DPP-4 inhibitor sold separately as Januvia) with metformin in a single twice-daily pill. Janumet XR offers once-daily extended-release dosing. It is one of the most widely prescribed oral combinations for type 2 diabetes globally, delivering combined A1C reduction of approximately 1.5 to 2.0 percent with a long safety track record from the TECOS cardiovascular outcomes trial.
What Janumet Contains
Janumet is manufactured by Merck. Active ingredients:
- Sitagliptin — a DPP-4 inhibitor that blocks the breakdown of incretin hormones GLP-1 and GIP, prolonging their action and enhancing glucose-dependent insulin release while suppressing glucagon after meals. Weight neutral, low hypoglycemia risk.
- Metformin hydrochloride — a biguanide that reduces hepatic glucose production, modestly improves insulin sensitivity, and slows intestinal glucose absorption. Foundational first-line type 2 diabetes therapy.
The two drugs work through distinct mechanisms — incretin enhancement and hepatic glucose suppression — making their effects additive and complementary.
Available Strengths
| Product | Sitagliptin | Metformin | Frequency |
|---|---|---|---|
| Janumet 50/500 | 50 mg | 500 mg (immediate-release) | Twice daily with meals |
| Janumet 50/1000 | 50 mg | 1,000 mg (immediate-release) | Twice daily with meals |
| Janumet XR 50/500 | 50 mg | 500 mg (extended-release) | Once daily (two tablets with evening meal) |
| Janumet XR 50/1000 | 50 mg | 1,000 mg (extended-release) | Once daily (two tablets with evening meal) |
| Janumet XR 100/1000 | 100 mg | 1,000 mg (extended-release) | Once daily (one tablet with evening meal) |
Maximum daily dose is sitagliptin 100 mg plus metformin 2,000 mg.
Dosing Instructions
- Janumet (immediate-release): take one tablet twice daily with meals to minimize gastrointestinal side effects.
- Janumet XR: take once daily with the evening meal. Swallow whole — do not crush, split, or chew (the extended-release matrix must remain intact).
- If a dose is missed and it is still the same day, take it as soon as remembered with food. Skip if it is nearly time for the next dose.
Who Janumet Is For
Janumet is approved for adults with type 2 diabetes as an adjunct to diet and exercise. Common scenarios:
- A1C remains above goal despite metformin monotherapy
- Already taking sitagliptin (Januvia) and metformin separately and want to consolidate
- Patient prefers an oral, weight-neutral, low-hypoglycemia-risk option
- Cardiovascular safety is desired without an established cardiovascular outcome benefit being required
It is not approved for type 1 diabetes, diabetic ketoacidosis, or pediatric patients under 18.
How Well Janumet Works
Pooled data from registration studies and the individual component evidence show:
- A1C reduction: approximately 1.5 to 2.0 percent in patients with poorly controlled type 2 diabetes (baseline A1C above 8.5 percent), and 0.8 to 1.2 percent in patients closer to goal.
- Weight change: approximately neutral — sitagliptin is weight-neutral, metformin causes a 1 to 2 kg loss in some patients.
- Fasting glucose: reduction of 30 to 50 mg/dL.
- Hypoglycemia risk: low when used without insulin or sulfonylureas — Janumet alone causes hypoglycemia in less than 2 percent of patients.
- Cardiovascular safety: the TECOS trial of sitagliptin in 14,671 patients with type 2 diabetes and cardiovascular disease showed cardiovascular non-inferiority and no signal of heart failure hospitalization (unlike saxagliptin).
For broader context on what these A1C reductions mean, see our explainer on A1C levels and targets.
Side Effects
| Side Effect | Source | Approximate Frequency |
|---|---|---|
| Nasopharyngitis | Sitagliptin | 6 to 8 percent |
| Upper respiratory tract infections | Sitagliptin | 5 to 6 percent |
| Diarrhea, nausea, abdominal pain | Metformin | 10 to 25 percent (often transient) |
| Headache | Both | 5 to 6 percent |
| Metallic taste | Metformin | 3 percent |
| Vitamin B12 deficiency | Metformin (long-term) | 5 to 10 percent at 5+ years |
| Hypoglycemia (when combined with insulin/sulfonylureas) | Both | Variable |
| Pancreatitis | Sitagliptin | Rare (less than 0.5 percent) |
| Severe joint pain | Sitagliptin (class effect) | Rare |
| Allergic reactions, angioedema | Sitagliptin | Rare |
| Lactic acidosis | Metformin | Very rare (3 to 10 per 100,000) |
| Bullous pemphigoid (skin) | Sitagliptin (class effect) | Very rare |
Most gastrointestinal symptoms from metformin improve within 2 to 4 weeks of starting or after switching to the extended-release Janumet XR formulation.
Contraindications and Warnings
- eGFR less than 30 mL/min/1.73 m squared: contraindicated (metformin).
- eGFR 30 to 45: sitagliptin requires dose reduction to 50 mg; existing Janumet users may continue with monitoring.
- eGFR less than 45 for new initiation: not recommended.
- Active diabetic ketoacidosis or type 1 diabetes.
- Severe hepatic impairment, acute or chronic metabolic acidosis, or chronic alcoholism.
- History of pancreatitis: use cautiously.
- Hold around iodinated contrast and major surgery.
- Pregnancy: not recommended in second or third trimester.
Drug Interactions
- Cationic drugs (cimetidine, dolutegravir, ranolazine) can increase metformin levels.
- Digoxin: sitagliptin can slightly increase digoxin AUC — monitor in patients near therapeutic limits.
- Insulin and sulfonylureas: increase hypoglycemia risk; dose reductions may be needed.
- Alcohol: increases lactic acidosis and hypoglycemia risk.
- Iodinated contrast: hold Janumet 48 hours before and after.
- Loop and thiazide diuretics: can reduce renal function — monitor in elderly patients.
Cost and Insurance
Without insurance, Janumet typically retails for $500 to $700 per month, and Janumet XR for similar. Merck’s manufacturer savings card can reduce eligible commercially insured patients’ out-of-pocket cost to as little as $5 per month for up to 12 months. Medicare and Medicaid patients are not eligible for the savings card but may qualify for Merck’s patient assistance program based on income.
Generic outlook: sitagliptin’s U.S. patent protection expires in 2026, with generic Januvia (sitagliptin) and generic Janumet expected to follow shortly. Prices may drop to $50 to $100 per month within 12 to 18 months of generic launch, significantly improving access.
Storage
- Store at controlled room temperature 68 to 77 degrees F (20 to 25 degrees C).
- Keep in original blister or bottle until use.
- Protect from moisture and heat.
- Do not crush, split, or chew Janumet XR.
Janumet vs Other DPP-4 + Metformin Combinations
| Combination | DPP-4 Inhibitor | Heart Failure Signal? | Renal Dosing |
|---|---|---|---|
| Janumet (sitagliptin + metformin) | Sitagliptin | No (TECOS neutral) | Adjust below eGFR 45 |
| Jentadueto (linagliptin + metformin) | Linagliptin | No (CARMELINA neutral) | No DPP-4 adjustment needed |
| Kombiglyze XR (saxagliptin + metformin) | Saxagliptin | Yes (SAVOR signal) | Adjust below eGFR 45 |
Among DPP-4 + metformin options, Janumet has the strongest cardiovascular safety evidence (TECOS) and the broadest prescribing experience globally. Jentadueto has the renal advantage. Kombiglyze XR is the least-preferred due to the saxagliptin heart failure signal.
Place in Modern Type 2 Diabetes Care
ADA Standards of Care 2024 recommend DPP-4 inhibitors as add-on options after metformin when weight-neutral, low-hypoglycemia oral therapy is preferred and cardiovascular outcome benefits are not the priority. Janumet sits in this niche reliably. For patients with established cardiovascular disease, heart failure, or chronic kidney disease, SGLT2 inhibitor combinations like Synjardy or Xigduo XR are preferred. For broader treatment context, see our treatment options page.
Practical Considerations for Patients
- Take Janumet IR with breakfast and dinner; take Janumet XR with dinner only.
- If starting from metformin alone, expect the additional 1.0 to 1.2 percent A1C reduction from sitagliptin to appear within 8 to 12 weeks.
- Monitor kidney function at least annually — earlier if you have CKD or are over 65.
- Stop and call your clinician for severe abdominal pain (especially radiating to the back), persistent vomiting, or yellowing of the skin or eyes — symptoms of pancreatitis.
- Inform any new clinician about Janumet before scheduled surgery, contrast imaging, or acute hospitalization.
- If long-term metformin user, ask about vitamin B12 testing every 1 to 2 years.
Janumet and Weight
Janumet is approximately weight-neutral. Sitagliptin causes no weight change, and metformin may cause modest weight loss of 1 to 2 kg in some patients. For larger weight loss, GLP-1 receptor agonists or SGLT2 inhibitors are more effective. See our discussions on Wegovy vs Ozempic for alternatives focused on weight reduction.
Janumet in the Pipeline
Generic sitagliptin and generic Janumet are expected within 12 to 24 months. This will likely shift prescribing patterns, especially in cost-sensitive populations and on formularies that currently prefer brand alternatives. Patients currently on Janumet should not need to change therapy when generics launch — switching is straightforward and bioequivalent.
The Bottom Line
Janumet combines sitagliptin and metformin in a single twice-daily tablet (or once-daily Janumet XR) for adults with type 2 diabetes. Combined A1C reduction of 1.5 to 2.0 percent comes with weight neutrality, low hypoglycemia risk, and the cardiovascular safety established in the TECOS trial. Common side effects are mild gastrointestinal symptoms and upper respiratory infections; serious but rare risks include pancreatitis, severe joint pain, and lactic acidosis. Janumet is contraindicated below eGFR 30 and should be held around contrast imaging and surgery. Generic sitagliptin expected in 2026 will likely reduce cost substantially. Talk to your clinician about whether Janumet’s profile — strong safety, modest A1C effect, weight neutrality — fits your diabetes plan, or whether an SGLT2-containing combination would offer additional cardiovascular or kidney benefits.
