DPP-4 inhibitors (gliptins) — patient guide

This page covers DPP-4 inhibitors — the family of type 2 diabetes tablets whose generic names end in “-gliptin”. Sitagliptin, vildagliptin, saxagliptin, linagliptin, and alogliptin all live on this page. The combination tablets that include a gliptin plus metformin or plus an SGLT2 inhibitor (Janumet, Galvumet, Komboglyze, Trajentamet, Glyxambi) live here too. If your tablet name is on the list below, this is your page.

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You have probably arrived here for one of three reasons. Your GP has added a gliptin to your metformin and the explanation was two sentences. You are already on a gliptin and someone in your circle is on a -flozin or on Ozempic and you are wondering whether you are on the right thing. Or you have just been handed a script for Trajenta or Galvus and the brand name means nothing to you, so you have typed it into a search bar to find out what it actually is.

All three are reasonable places to be standing. Let me give you the longer version of each conversation.

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Find your medicine

Generic name	Common brand names	Strengths	How often
Sitagliptin	Januvia, Janumet (with metformin), Janumet XR, generics	25 / 50 / 100 mg	Once daily
Vildagliptin	Galvus, Galvumet (with metformin)	50 mg	Twice daily
Saxagliptin	Onglyza, Komboglyze (with metformin), Qtern (with dapagliflozin)	2.5 / 5 mg	Once daily
Linagliptin	Trajenta, Trajentamet (with metformin), Glyxambi (with empagliflozin)	5 mg	Once daily
Alogliptin	Nesina	6.25 / 12.5 / 25 mg	Once daily

Vildagliptin (Galvus, Galvumet) is the only twice-daily gliptin in Australia. The others are once-daily. If your tablet says Galvus or Galvumet and your script says morning and night, that is correct, not a pharmacy error.

Closely related families worth knowing exist — metformin (the usual partner medicine), SGLT2 inhibitors (names end in -flozin — Jardiance, Forxiga, Steglatro), GLP-1 receptor agonists (Ozempic, Trulicity, Mounjaro, Saxenda, Victoza), sulfonylureas (gliclazide, glimepiride, glibenclamide), and insulin. Each has its own page or will soon. Most people on a gliptin are also on metformin, often as a combination tablet — see the list below.

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What it treats

DPP-4 inhibitors are licensed in Australia for type 2 diabetes — usually added on top of metformin, or used as an alternative when metformin is not tolerated. That is the only on-label use for this class. There is no credible off-label use worth including on a patient flyer.

The headline guidelines are the RACGP T2DM guidelines, eTG Endocrinology, the Australian Diabetes Society position statements, and the ADA/EASD 2022 consensus. These are the documents your GP is working from. A typical sequence in current Australian practice is metformin first, then either an SGLT2 inhibitor, a GLP-1 receptor agonist, or a DPP-4 inhibitor as the second agent, chosen based on your kidney function, cardiovascular history, weight goals, and what your body tolerates.

A note on where this class sits. DPP-4 inhibitors are a settled, well-tolerated tablet class. In modern Australian practice, SGLT2 inhibitors and GLP-1 receptor agonists are more often chosen as the second agent after metformin because they offer cardiovascular, kidney, and weight benefits the DPP-4 class does not. That does not mean a gliptin is the wrong choice for you. There are several picture-specific reasons a gliptin is the right second agent — including kidney function (linagliptin needs no dose adjustment), intolerance of the newer classes, cost or supply considerations, and the simple fact that it has worked steadily for you for years. The point is: if you are on a gliptin, you are on a tablet that does its job reliably. The right question is not should I be on something else but given my situation, is this still the best fit? That is the conversation we have in the consult.

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The basics

1. Take it as directed. Once daily for sitagliptin, saxagliptin, linagliptin, alogliptin. Twice daily for vildagliptin (Galvus / Galvumet).
2. Food does not matter for absorption. Take it with or without meals — pick a time you will remember.
3. Watch for the class red flags below — severe abdominal pain, new disabling joint pain, new blistering rash, yellowing of skin or eyes (vildagliptin in particular).
4. If you are also on metformin in a combination tablet (Janumet, Galvumet, Komboglyze, Trajentamet), the metformin sick-day rule still applies — pause during vomiting, severe gastro, fever where fluids will not stay down, before CT scans with contrast, and before major surgery.
5. Message us before starting anything new — supplements, herbs, big diet changes, new medicines from another doctor. Some interact.

Everything else — mechanism, side effects in detail, the integrative angle, the kidney-and-heart notes — is below.

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Sick day rules — when to pause

DPP-4 inhibitors on their own rarely need to be paused for a short illness. The pause rules are mostly about the partner medicines in your regimen.

If you are on a combination tablet that includes metformin (Janumet, Janumet XR, Galvumet, Komboglyze, Trajentamet), follow the metformin sick-day rule. Pause the tablet for any of these lasting more than a few hours:

• Vomiting
• Severe diarrhoea
• Fever where you cannot keep fluids down
• Heavy sweating with poor fluid intake
• Any acute serious illness — chest infection requiring hospital, suspected sepsis, severe pain

Also pause the metformin-combo tablet:

• 24-48 hours before and after a CT scan with iodinated contrast if your eGFR is below 60
• 24-48 hours before major surgery (the anaesthetist usually confirms)

If you are also on a sulfonylurea (gliclazide, glimepiride, glibenclamide) or insulin and you cannot eat normally, the dose of those agents is reviewed — often reduced — to avoid low blood sugar. Message us; do not guess on your own.

If you are on the gliptin alone and you are well enough to keep fluids down, continue. Restart the combination tablet 24-48 hours after the illness, when you are eating, drinking, and well.

If you are not sure, message.

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Tap any section below to expand the detail.

How does it work?

When you eat a meal, your gut releases two hormones called GLP-1 and GIP. Together they are known as the “incretin” hormones. They signal your pancreas to release insulin in proportion to the meal, and they reduce glucagon (the hormone that tells your liver to release stored glucose). The body breaks both hormones down quickly via an enzyme called dipeptidyl peptidase-4 (DPP-4) — usually within minutes.

DPP-4 inhibitors block that enzyme. The body’s own GLP-1 and GIP stick around longer, the meal-time insulin response is a bit stronger, and the glucagon response is a bit weaker. The result is modestly lower blood sugar — typically about 0.5-0.8% off the HbA1c.

Three useful properties fall out of that mechanism:

• The effect is glucose-dependent — the incretin signal only fires meaningfully when blood sugar is up. On its own, a gliptin is unlikely to cause hypoglycaemia.
• The effect is weight-neutral — the incretins are not at the level where they meaningfully suppress appetite (that is the territory of the injectable GLP-1 receptor agonists like Ozempic, which provide a much larger and longer-acting GLP-1 signal).
• The effect is modest but reliable. The HbA1c drop is consistent across the class.

There is one mechanistic nuance worth knowing. DPP-4 has other substrates in the body besides GLP-1 and GIP — including some involved in immune signalling, skin biology, and connective tissue. That is the plausible mechanistic explanation for the rare class signals: bullous pemphigoid (a blistering skin condition), severe joint pain, and the pancreatitis signal. The signals are rare. The mechanisms are biologically reasonable. The risk-benefit balance still sits clearly in favour of treatment when the medicine is doing its job.

Side effects in detail

Common — usually mild

• Headache — most common; usually settles.
• Nasopharyngitis (cold-like symptoms, sore throat, runny nose) — reported a little more often on gliptins than placebo in the trials. Usually mild.
• Mild stomach upset — much less than with metformin, but a small number of people get nausea or mild gut discomfort.

Less common but worth watching for

• Hypoglycaemia (low blood sugar) when combined with a sulfonylurea (gliclazide, glimepiride, glibenclamide) or insulin. A gliptin on its own carries a low risk; combined with either of those, the risk goes up meaningfully and the dose of the sulfonylurea or insulin is usually reduced to compensate.
• Skin reactions — rash, itch. Most settle. Persistent or worsening rash warrants review.
• Mild rise in liver enzymes (vildagliptin in particular) — picked up on the routine monitoring. Most resolve without stopping; significant rises mean stopping.

Rare but serious — stop the medicine and seek review

• Acute pancreatitis. Small class signal. Severe abdominal pain, often radiating through to the back, often with nausea and vomiting. Stop the gliptin and seek urgent medical review. The decision about whether to restart any incretin-related medicine afterwards is shared with a specialist.
• Severe joint pain. FDA class warning (2015) — most often reported with sitagliptin and linagliptin. Onset can be anywhere from a day to years after starting. Usually reversible within weeks of stopping. New disabling joint pain on a gliptin is worth reporting rather than putting down to age.
• Bullous pemphigoid. A rare blistering skin condition; the class-wide odds ratio in the Douros et al. analysis (Ann Intern Med 2019) was about 2, with vildagliptin disproportionately represented. Any new blistering rash, especially on the limbs or trunk, warrants review.
• Severe allergic reaction including angioedema. Rare but reported. Swelling of the face, lips, tongue, or throat — call 000 if the airway is involved.
• Severe liver injury (vildagliptin). Yellowing of the skin or eyes, dark urine, persistent nausea, right-upper-quadrant pain — stop and seek review.

Heart-failure note (saxagliptin specifically). The SAVOR-TIMI 53 trial (NEJM 2013) showed a modest signal for increased heart-failure hospitalisation in patients on saxagliptin compared with placebo, in a population with high cardiovascular risk. This signal was not seen for sitagliptin in TECOS (NEJM 2015), alogliptin in EXAMINE (NEJM 2013), or linagliptin in CARMELINA (JAMA 2019). It is a saxagliptin-specific finding rather than a class-wide one. The Australian Diabetes Society practical preference is to choose a different gliptin in patients with established heart failure. If you have heart failure and you are on saxagliptin, that is a planned review with your GP, not an emergency.

Drugs, food, and alcohol

Tell us or your pharmacist before combining with:

• Sulfonylureas (gliclazide, glimepiride, glibenclamide) — adding a gliptin increases low-blood-sugar risk. The sulfonylurea dose is often reduced when starting a gliptin.
• Insulin — same principle. The insulin dose is often reduced when starting a gliptin to avoid low blood sugar.
• ACE inhibitors (perindopril, ramipril, lisinopril, enalapril, captopril) — case reports suggest a small increase in angioedema risk when combined with a DPP-4 inhibitor. Uncommon, not a contraindication, but worth knowing if you develop any facial swelling.
• Strong CYP3A4 inhibitors (ketoconazole, itraconazole, clarithromycin) — saxagliptin dose should be reduced to 2.5 mg per day when co-prescribed.
• Strong CYP3A4 inducers (rifampicin, carbamazepine, phenytoin) — can reduce saxagliptin and linagliptin levels. Clinical relevance is modest; check with your prescriber if you are starting one.

Food. No restrictions. Take your gliptin at a time you will remember — with or without meals.

Alcohol. Light to moderate intake is generally compatible. Heavy intake adds load on the pancreas and on the liver — both relevant to DPP-4 safety flags. If you are on vildagliptin in particular, heavier alcohol amplifies the small hepatotoxicity signal.

Generic substitution at the pharmacy. Generic versions of sitagliptin, vildagliptin, saxagliptin, and linagliptin are appearing as the original patents expire. They are bioequivalent. If your pharmacist offers a cheaper generic, that is fine. The one swap worth flagging: a brand swap is fine, but a swap between different gliptins (for example sitagliptin to linagliptin) is a medication change, not a generic substitution, and would only be made by your prescriber.

Monitoring — what blood tests and when

The standard monitoring picture for someone on a gliptin in Australia looks like this:

• Baseline before starting: eGFR (kidney function), HbA1c, fasting glucose, liver function, full blood count.
• Vildagliptin specifically — extra liver monitoring. LFTs before starting, then 3-monthly during the first year, then yearly thereafter per current AMH. Confirm cadence at script time with your pharmacist or GP.
• HbA1c every 3 months until on a stable dose with a stable result, then every 6 months.
• eGFR annually — sooner if you have CKD, are on combinations of other kidney-relevant medicines, or have been acutely unwell. Renal dose adjustment thresholds:
  • Sitagliptin — eGFR 30-50 use 50 mg/day; eGFR <30 use 25 mg/day.
  • Saxagliptin — eGFR <45 use 2.5 mg/day.
  • Linagliptin — no renal adjustment required at any eGFR.
  • Alogliptin — eGFR 30-60 use 12.5 mg/day; eGFR <30 use 6.25 mg/day.
  • Vildagliptin — current AMH guidance is dose adjustment in moderate-to-severe renal impairment; confirm at script time.
• Vitamin B12 annually if you are also on metformin (which is the usual situation) — covered on the metformin page.

Message us if you: start a new medicine (including over-the-counter or supplements), get a gastro illness, plan a CT scan with contrast or major surgery, or notice any of the class red flag symptoms above.

Stopping or pausing

Do not stop on your own without talking to us — but pausing for sick days (above) when on a metformin-combination tablet is part of normal use, not stopping.

• Sick day pauses apply if you are on a metformin-containing combination tablet. Resume when eating, drinking, and well — usually 24-48 hours.
• If side effects are the issue (joint pain, blistering rash, persistent nausea, abnormal LFTs on vildagliptin), we usually stop the medicine and switch to a different glucose-lowering option. The HbA1c drop from a gliptin is replaceable — that part of the picture is fixable.
• If you have severe abdominal pain or any class red flag, stop and seek review the same day.
• Before major surgery, follow the anaesthetist’s instructions about the combination tablet. The DPP-4 component alone does not generally need to be paused for surgery; the metformin component does.

Pregnancy and breastfeeding

DPP-4 inhibitors are not recommended in pregnancy. Safety data is limited, and there is no need to use them — insulin has decades of pregnancy safety data and is the default agent for glucose control in pregnancy.

If you are planning a pregnancy or have just found out, message us early. The standard plan is to switch from any oral diabetes regimen (gliptin, metformin, sulfonylurea, SGLT2 inhibitor, GLP-1 agonist) to insulin under joint care between your GP, your endocrinologist, and your obstetric team. The RANZCOG and ADIPS consensus on gestational diabetes and pre-existing diabetes in pregnancy is the reference document.

Breastfeeding data on gliptins is limited. The usual approach is to keep insulin on board through breastfeeding and reassess once you have weaned.

If you’re on a combination tablet

Many people on a gliptin are actually on a combination tablet — a gliptin plus a second diabetes medicine in one pill, which reduces the number of tablets per day and often the PBS cost.

Gliptin + metformin:

• Janumet / Janumet XR = sitagliptin + metformin
• Galvumet = vildagliptin + metformin
• Komboglyze = saxagliptin + metformin
• Trajentamet = linagliptin + metformin

Gliptin + SGLT2 inhibitor (two glucose-lowering pathways combined):

• Glyxambi = linagliptin + empagliflozin
• Qtern = saxagliptin + dapagliflozin
• Steglujan = sitagliptin + ertugliflozin

Everything on this page applies to the gliptin portion of your combination tablet. The other component has its own side effects, monitoring requirements, and sick day rules — the metformin page is here and the SGLT2 page is here. Ask us, and we will walk through the combination specifically for you.

Cost

All five DPP-4 inhibitors and the main combination tablets are listed on the PBS for type 2 diabetes. From 1 January 2026, the PBS co-payment ceiling is:

• General patient: up to $25.00 per script
• Concession card holder: up to $7.70 per script

Generic versions of sitagliptin, vildagliptin, saxagliptin, and linagliptin are appearing as the original patents expire — some generic gliptins now sit under the co-payment threshold. Pricing varies between pharmacies. Confirm with your pharmacist; they can show you the cheapest equivalent. Alogliptin (Nesina) is lower-volume in Australian dispensing and supply at any given pharmacy may be intermittent — worth checking before assuming a same-day pickup.

(MBS / PBS items verified 2026-05-25 via WebSearch — workspace egress to mbsonline.gov.au + pbs.gov.au still blocked; spot-check confirms current.)

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This is not a cop-out — it’s the reason the consult exists. You are biochemically unique. Anything I write here may apply to you completely, in part, or not at all, and there is no honest way to know in advance. Some people are allergic to peanuts; your biochemistry has its own particulars, and uncovering them is its own work — done by experimenting on yourself, with informed starting points. Everything on this page is general in nature for exactly that reason. The specific version of any of this is a conversation, not an article.

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The integrative view

Most patients on a gliptin are also on metformin, and most are working on the underlying terrain in some form — eating differently, moving more, sleeping better, managing stress. That work matters. A gliptin (or any diabetes tablet) is one lever; the terrain underneath it is another. The two work together.

Two principles I work from. First: the tablet has its job — modestly lowering HbA1c through the incretin pathway — and it does that job reliably. Second: lifestyle change is the lever that addresses the upstream picture (insulin resistance, visceral adiposity, sleep apnoea, cortisol patterns) that the tablet does not directly touch. Combined, they outperform either alone.

Strong evidence — these reliably help glucose control

These are interventions where the data is solid enough to discuss with any patient on a gliptin. Effect sizes below are approximations from clinical trials; your individual response will vary.

• DASH-style or Mediterranean-style eating pattern. Vegetables, fruit, legumes, whole grains, oily fish, olive oil, nuts. Both patterns have multi-trial data showing improvements in HbA1c, blood pressure, and cardiovascular outcomes. The Mediterranean pattern in particular has strong data in metabolic syndrome.
• Low-glycaemic-index / carbohydrate-quality approach. Less about cutting carbs entirely, more about choosing the slower-absorbing versions — legumes, oats, intact whole grains, vegetables — over the fast ones (white bread, sugary drinks, refined cereals). HbA1c reductions of 0.3-0.5% are typical with sustained change.
• Resistance training, 2-3 sessions per week. Improves insulin sensitivity per minute of training more than aerobic exercise does. A useful fact for people who say “I don’t have time for an hour of cardio.” Twenty minutes of weights twice a week meaningfully shifts the picture.
• Aerobic exercise, 150 minutes per week. Brisk walking, cycling, or equivalent. Synergistic with resistance training.
• Treating sleep apnoea if present. Sleep deprivation and untreated obstructive sleep apnoea worsen insulin resistance measurably. Snoring + daytime tiredness + observed pauses in breathing during sleep is worth a sleep study.
• Time-restricted eating. Emerging evidence is encouraging — an 8-10 hour eating window appears to improve glycaemic control and weight in T2DM without complex tracking. Starts at closing the kitchen 3 hours before bed.

Moderate evidence — likely helpful

• Magnesium-rich foods (leafy greens, nuts, seeds, legumes, dark chocolate). Adequate magnesium supports insulin signalling. Food first; supplementation only if there is a specific reason and a measured deficit.
• Vitamin D adequacy. Independent association with glycaemic control. Check level; supplement if low.
• Stress reduction practices — slow breathing (~6 breaths/minute), meditation, yoga. Modest direct glucose effect; bigger indirect effect via cortisol patterns and food choices.

Limited or emerging evidence

• Cinnamon, fenugreek, bitter melon, gymnema. Modest evidence, considerable individual variation. If they are already part of your eating culture, that is fine. Supplement form is low-confidence; I will not talk you out of it but I would not recommend buying it.
• Omega-3 (fish oil), 1-3 g EPA/DHA daily. Cardiovascular protection more than glucose effect. The high-EPA REDUCE-IT trial showed benefit in high-triglyceride patients.
• Berberine. Activates a similar cellular pathway (AMPK) to metformin and has small-trial evidence in PCOS, lipids, and glycaemic control. It is not a substitute for metformin or for a gliptin in established T2DM. Two cautions: berberine inhibits CYP3A4 and interacts with several common medicines (including some statins and blood thinners), and it has its own stomach side effects. Not safe in pregnancy. If you are considering it on top of your current regimen, that is the conversation we have in the consult — not a solo experiment.

Specific to being on a gliptin

• Vitamin B12 — if you are also on metformin (which is the usual partner), annual measurement after the first 12 months. Long-term metformin lowers B12 in 10-30% of people; deficiency can mimic diabetic nerve damage.
• Hydration. Stay genuinely hydrated. Particularly relevant if you are on a combination tablet that includes metformin.
• Watch the partner medicine. Most of the sick-day discipline, drug interactions, and monitoring on this page applies to whichever medicine is partnered with your gliptin (most often metformin). The gliptin itself is the quieter half of the combination.

The terrain conversation

DPP-4 inhibitors do not directly touch the underlying physiology that produced your type 2 diabetes — insulin resistance, visceral adiposity, sleep architecture, food environment, stress and cortisol patterns. Lifestyle change does. That is not a criticism of the medicine; it is a description of how each lever works. The medicine modestly lowers your meal-time glucose excursion. Lifestyle change addresses the upstream picture. The two are complementary, not competing.

For some patients on a gliptin — particularly those who started early in the diabetes journey, with substantial sustained lifestyle change — the HbA1c can come down enough that the medicine becomes unnecessary. For others — particularly those further along with established diabetes — the medicine continues to do useful work on top of the lifestyle picture. We work that out together with monitoring, not on your own.

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Track these between now and your next visit

• Home blood glucose readings if you have a meter — fasting and 2-hours-post-meal, a few times a week. Bring the log.
• Any new symptoms — severe abdominal pain (urgent), new disabling joint pain, new blistering rash, yellowing of skin or eyes, persistent nausea, swelling of face / lips / tongue.
• Anything new you have started — supplements, herbs, big diet changes, new medicines from another doctor.
• Sick days, contrast scans, or surgery since the last visit, and whether you paused any combination tablet.
• Your weight, your exercise routine, your sleep pattern — short notes, not a spreadsheet. The trajectory matters more than the precision.

Bring the list to your review appointment.

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This is general information, not personal medical advice. Every patient is different. Decisions about your medicines — which one, what dose, when to stop, what to combine with — are made with the doctor who prescribed them. If anything on this page appears to contradict advice from your treating doctor, follow your doctor; they have context about your situation that this page cannot.

Reading this page does not establish a doctor-patient relationship with Dr Hoebing Lo. If you are not a current patient, please discuss your medicines with your own GP, specialist, or pharmacist.

About the integrative content. The lifestyle, dietary, and complementary recommendations on this page summarise current published research. Effect sizes are approximations from clinical studies — your individual response will vary, and real-world results are commonly smaller than trial results because day-to-day life differs from study conditions. Supplements and herbal products are not interchangeable with prescribed medication and can interact with it. Talk to your doctor and pharmacist before starting any new supplement, herbal product, or significant change in diet.

Currency. This page reflects clinical practice as of the last-reviewed date. Medicine evolves; specific details may date between reviews. Pricing shown is indicative; confirm with your pharmacist.

No commercial relationships. Dr Hoebing Lo has no financial or commercial relationship with the manufacturer of any medicine, brand, or supplement mentioned on this page.

Emergencies. If you have severe abdominal pain (especially with nausea and vomiting), swelling of the face / lips / tongue / throat, severe widespread blistering rash, or any sudden severe new symptom — call 000 or go to your nearest emergency department. Do not wait, and do not message us first.