Sitagliptin: what it treats, how to take it, side effects
Last updated September 3, 2026.
Sitagliptin is a DPP-4 inhibitor - it increases the natural substances that lower blood sugar when it is high. You may know it as Januvia. It is a once-a-day tablet for type 2 diabetes in adults, and most people feel nothing on it at all.
What does it treat?
High blood sugar in adults with type 2 diabetes, alongside diet and exercise. It is not used to treat type 1 diabetes.
How do you take it?
One tablet once a day, with or without food, at the same time every day. The label's standard dose is 100 mg; with moderate kidney impairment it drops to 50 mg, and with severe kidney impairment or dialysis, 25 mg - the kidneys set the dose, which is why the blood-work schedule matters. It controls blood sugar but does not cure diabetes: keep taking it even when you feel well, and never stop without your doctor. Missed dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: stuffed or runny nose, sore throat, headache, diarrhea, and nausea.
- Serious: stop taking it and call your doctor immediately for the pancreatitis cluster - fever, nausea, vomiting, loss of appetite, and ongoing pain that begins in the upper left or middle of the stomach but may spread to the back. Also stop-and-call: the heart failure cluster of shortness of breath, unusual tiredness, rapid weight gain, and swelling of the feet or ankles; blistering or peeling skin; joint pain; and allergic reactions with itching, rash, hives, swelling of the face, lips, tongue, or throat, or trouble breathing or swallowing.
Who should not take it?
Anyone with type 1 diabetes. Flag past pancreatitis, gallstones, high triglycerides, and heavy alcohol use - all pancreatitis risks - plus heart failure and kidney disease. If you are also on a sulfonylurea or insulin, the label warns low blood sugar becomes more likely, and doses of those may need adjusting. Fever, infection, and injury change blood sugar, so sick-day rules come from your doctor in advance. If you become pregnant, call your doctor.
When is it an emergency?
Severe stomach pain radiating to your back with vomiting - the pancreatitis picture - means stopping the drug and getting immediate care. Trouble breathing or swelling of the face or throat is a 911 call. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why did my doctor check my kidneys before prescribing sitagliptin?
Because the kidneys set the dose. The label's standard is 100 mg once daily, but it drops to 50 mg with moderate kidney impairment and 25 mg with severe impairment or dialysis. The blood work is the dosing math, not a formality.
What is the pancreatitis warning about?
MedlinePlus is specific: ongoing pain that begins in the upper left or middle of the stomach and may spread to the back, with fever, nausea, vomiting, or loss of appetite, means stop taking sitagliptin and call your doctor immediately. It is the one symptom on this drug that never waits for an appointment.
Can I drink alcohol while taking sitagliptin?
Flag your history honestly. MedlinePlus lists heavy alcohol use among the things to disclose before starting, because it raises the pancreatitis risk the drug also carries. Whether any amount is fine for you depends on your history - ask your doctor directly.
Why is sitagliptin not for type 1 diabetes?
The mechanism needs a working pancreas. Sitagliptin increases the natural substances that lower blood sugar by prompting insulin release - in type 1 diabetes the insulin-producing cells are gone, so there is nothing to prompt. Type 1 runs on insulin itself.
Does sitagliptin cause low blood sugar?
On its own it works through substances that act when blood sugar is high, so the risk is low. The label warns the picture changes in combination: with a sulfonylurea or insulin, low blood sugar becomes more likely, and those doses may need to come down. Either way, MedlinePlus says to learn the symptoms of low and high blood sugar and what to do about them.
What happens if I miss a dose of sitagliptin?
Take it as soon as you remember, unless it is almost time for the next one - then skip it and never double up. One missed dose is a small event with a once-daily drug; a pattern of misses shows up in your A1C.