Januvia Side Effects: What to Expect and When to Call Your Doctor

Januvia (sitagliptin) is generally considered one of the better-tolerated diabetes medications on the market. In clinical trials, its overall side effect rate was similar to placebo when used alone or with metformin. But like any medication, Januvia does have potential side effects — ranging from mild and common to rare but serious. Here's what you need to know.

Most Common Januvia Side Effects

The most frequently reported side effects of Januvia — affecting 5% or more of patients in clinical trials — are:

Upper respiratory tract infection: Cold-like symptoms, cough, sore throat. Generally mild and self-resolving. Evidence on whether DPP-4 inhibitors truly increase infection risk is mixed.

Nasopharyngitis: Stuffy or runny nose, sneezing — essentially a common cold. Usually goes away on its own.

Headache: Mild headaches that typically improve with time. Drinking adequate water and taking Januvia with food may help.

Other mild side effects that some patients experience include abdominal pain, nausea, diarrhea, and constipation.

Does Januvia Cause Low Blood Sugar (Hypoglycemia)?

One of Januvia's key advantages is its low hypoglycemia risk when used alone or with metformin. Because Januvia only stimulates insulin release when blood sugar is elevated (glucose-dependent mechanism), the risk of dropping blood sugar too low is minimal as monotherapy.

However, when Januvia is combined with a sulfonylurea (like glipizide or glyburide) or with insulin, hypoglycemia risk increases. In those cases, your doctor may need to lower the dose of the sulfonylurea or insulin to reduce the risk. Symptoms of low blood sugar include:

Shakiness, sweating, or trembling

Confusion, dizziness, or difficulty concentrating

Rapid heartbeat or hunger

In severe cases: loss of consciousness (requires emergency care)

Serious Side Effects to Watch For

While uncommon, the following serious side effects have been reported with Januvia and warrant immediate medical attention:

Pancreatitis: Severe, persistent abdominal pain (sometimes radiating to the back) with or without vomiting is the hallmark symptom. Several post-marketing reports of pancreatitis, including fatal cases, have been reported with sitagliptin. Stop taking Januvia and call your doctor immediately if you experience these symptoms.

Acute kidney injury: Post-marketing reports of sudden kidney failure, sometimes requiring dialysis. Call your doctor if you notice significant decreases in urination, swelling in legs/ankles, or unusual fatigue.

Severe joint pain (arthralgia): The FDA added a warning in 2015 after reports of severe, disabling joint pain in patients taking DPP-4 inhibitors including Januvia. In reported cases, substantial reduction in activity level occurred; some patients were hospitalized. Symptoms can appear from one day to years after starting the medication. Joint pain typically resolves when Januvia is discontinued.

Serious allergic reactions: Anaphylaxis, angioedema (large, hive-like swelling of the face, lips, tongue, or throat), and severe skin reactions including Stevens-Johnson syndrome have been reported. Stop Januvia immediately and seek emergency care if you develop sudden breathing difficulty, throat swelling, or widespread skin reactions.

Bullous pemphigoid: A rare skin condition that causes large fluid-filled blisters. If you develop blisters or skin erosions while on Januvia, contact your doctor promptly.

Heart failure risk: The TECOS cardiovascular outcomes trial showed Januvia had neutral effects on heart failure hospitalization (unlike saxagliptin and alogliptin, which showed increased risk). However, patients with known heart failure risk factors should be monitored. Tell your doctor immediately if you experience shortness of breath, difficulty breathing while lying down, rapid weight gain, or swelling in legs.

Does Januvia Cause Weight Gain?

No. Januvia is considered weight-neutral — clinical trials did not show meaningful weight gain with sitagliptin. In some studies, patients on placebo lost slightly more weight than patients on Januvia. This weight neutrality is one of Januvia's advantages compared to some other diabetes medications (like insulin or sulfonylureas) that are associated with weight gain.

When Should I Call My Doctor?

Call your doctor right away — or go to the emergency room — if you experience:

Severe abdominal pain (possible pancreatitis)

Swelling of the face, lips, tongue, or throat (possible angioedema)

Severe, disabling joint pain

Signs of serious allergic reaction (hives, difficulty breathing)

Blisters or skin breakdown (possible bullous pemphigoid)

Signs of severe low blood sugar (if taking Januvia with insulin or sulfonylureas)

Signs of kidney problems (decreased urination, ankle swelling, unusual fatigue)

For information on drug interactions that may affect Januvia's safety profile, see our guide: Januvia Drug Interactions: What to Avoid and What to Tell Your Doctor.

If side effects or other issues are making it hard to stay on Januvia and you need help finding it at a pharmacy, medfinder can locate a pharmacy near you that has your prescription in stock.