Short answer: In the label's placebo-controlled trials, the side effects seen in at least 5% of people and more often than on placebo were stuffy or runny nose with sore throat (5.2% vs 3.3% on its own), upper respiratory infection and headache. Low blood sugar was more common when Januvia was added to a sulfonylurea or insulin. Januvia has no boxed warning; pancreatitis is its first listed serious risk.
What Januvia is approved for: Januvia is a DPP-4 inhibitor approved, along with diet and exercise, to improve blood sugar control in adults with type 2 diabetes (section 1). It is not for type 1 diabetes, and it has not been studied in people who have had pancreatitis.
Source
JANUVIA (sitagliptin) tablets, for oral use, prescribing information and Medication Guide. Merck Sharp & Dohme. DailyMed, version published November 17, 2025. DailyMed setid f85a48d0-0407-4c50-b0fa-7673a160bf01
No. The current Januvia label has no boxed warning.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Januvia.
| Study and adverse reaction | JANUVIA 100 mg arm, n (%) | Placebo arm, n (%) |
|---|---|---|
| Monotherapy (18 or 24 weeks), N = 443 vs 363: Nasopharyngitis | 23 (5.2) | 12 (3.3) |
| With pioglitazone (24 weeks), N = 175 vs 178: Upper Respiratory Tract Infection | 11 (6.3) | 6 (3.4) |
| With pioglitazone (24 weeks): Headache | 9 (5.1) | 7 (3.9) |
| With metformin + rosiglitazone (18 weeks), N = 181 vs 97: Upper Respiratory Tract Infection | 10 (5.5) | 5 (5.2) |
| With metformin + rosiglitazone (18 weeks): Nasopharyngitis | 11 (6.1) | 4 (4.1) |
| With glimepiride (+/- metformin) (24 weeks), N = 222 vs 219: Nasopharyngitis | 14 (6.3) | 10 (4.6) |
| With glimepiride (+/- metformin) (24 weeks): Headache | 13 (5.9) | 5 (2.3) |
Number of patients (%), intent-to-treat population. Each study is listed with its own groups: JANUVIA 100 mg or placebo added to the same background medicine. Nasopharyngitis means a stuffy or runny nose with sore throat.
| Add-on study (24 weeks) and measure | JANUVIA 100 mg arm | Placebo arm |
|---|---|---|
| Glimepiride (+/- metformin), N = 222 vs 219: Overall, n (%) | 27 (12.2) | 4 (1.8) |
| Glimepiride (+/- metformin): Rate (episodes/patient-year) | 0.59 | 0.24 |
| Glimepiride (+/- metformin): Severe, n (%) | 0 (0.0) | 0 (0.0) |
| Insulin (+/- metformin), N = 322 vs 319: Overall, n (%) | 50 (15.5) | 25 (7.8) |
| Insulin (+/- metformin): Rate (episodes/patient-year) | 1.06 | 0.51 |
| Insulin (+/- metformin): Severe, n (%) | 2 (0.6) | 1 (0.3) |
Based on all reports of symptomatic low blood sugar; a glucose reading was not required. Rate counts every episode, so one person can have several. Severe means needing medical help, or with reduced consciousness or a seizure.
With metformin and rosiglitazone, through week 54: upper respiratory infection 15.5% vs 6.2% on placebo, stuffy or runny nose 11.0% vs 9.3%, swelling of the legs or feet (peripheral edema) 8.3% vs 5.2%, and headache 5.5% vs 4.1%.
Stomach side effects in four pooled trials: abdominal pain 2.3% vs 2.1% on placebo, nausea 1.4% vs 0.6%, and diarrhea 3.0% vs 2.3%.
Low blood sugar in four pooled trials without a sulfonylurea or insulin: 1.2% on Januvia 100 mg vs 0.9% on placebo.
Across 19 pooled trials (10,246 people), acute pancreatitis occurred at 0.1 per 100 patient-years in both the sitagliptin and control groups.
White blood cell count rose by about 200 cells/microL vs placebo, from a mean of about 6,600; the label says this is not considered clinically relevant.
Reported after approval, with frequency unknown: allergic reactions including anaphylaxis, angioedema and Stevens-Johnson syndrome; liver enzyme rises; pancreatitis; kidney failure; severe joint pain; bullous pemphigoid; constipation; vomiting; headache; muscle pain; mouth ulcers; and rhabdomyolysis.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Pancreatitis. Acute pancreatitis, including fatal and non-fatal hemorrhagic or necrotizing pancreatitis, has been reported after approval. People are watched for signs after starting, and Januvia is stopped promptly if pancreatitis is suspected. Whether a past pancreatitis raises the risk is not known.
Heart failure. Heart failure was linked to two other DPP-4 inhibitors in heart outcome trials. Risks and benefits are weighed before starting in people at risk, such as those with past heart failure or kidney problems, and they are watched for symptoms.
Acute kidney failure. Worsening kidney function, including acute kidney failure sometimes needing dialysis, has been reported, some in people given doses too high for their kidney function. Kidney function is checked before starting and from time to time after.
Low blood sugar with insulin or a sulfonylurea. Low blood sugar was more common when Januvia was added to insulin or a sulfonylurea, so a lower dose of those medicines may be needed.
Allergic reactions. Serious allergic reactions, including anaphylaxis, angioedema and skin peeling conditions such as Stevens-Johnson syndrome, have been reported, mostly within the first 3 months and some after the first dose. Januvia is stopped if one is suspected.
Severe and disabling joint pain. Severe joint pain has been reported with DPP-4 inhibitors, starting anywhere from one day to years after starting. It eased after stopping, and in some people came back on restarting.
Bullous pemphigoid. A blistering skin condition needing hospital care has been reported with DPP-4 inhibitors. New blisters or skin erosions are reported to the prescriber, and Januvia is stopped if bullous pemphigoid is suspected.
From the Medication Guide that comes with Januvia:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.