Janumet dosage, forms, and strengths

Janumet is a brand-name prescription drug used to control blood sugar in people diagnosed with Type 2 diabetes mellitus. Janumet combines metformin hydrochloride with sitagliptin phosphate. Metformin is the first-line treatment for Type 2 diabetes and is frequently taken with other antidiabetic agents. Sitagliptin belongs to a new family of drugs called dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors). Together, the two drugs bring blood glucose levels down by increasing both insulin production and insulin sensitivity, decreasing the absorption of sugar from food, and reducing glucose production in the liver. 

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Janumet forms and strengths

Janumet tablets come in two dose strengths. The lower dose is used for people not currently taking metformin or on a lower dose of metformin while the higher dose is appropriate for people already on metformin therapy.

• Tablets: 50 mg of sitagliptin/500 mg of metformin HCl; 50 mg of sitagliptin/1000 mg of metformin

Janumet is also available in an extended-release format, Janumet XR, combining immediate-release sitagliptin with extended-release metformin. 

Janumet dosage for adults

Janumet is taken as a tablet twice per day to control blood sugar levels in adults with Type 2 diabetes. Janumet is not used to treat Type 1 diabetes or diabetic ketoacidosis, a life-threatening complication of Type 1 diabetes that only rarely occurs in people with Type 2 diabetes.

Source: Epocrates

Janumet dosage for Type 2 diabetes

Janumet is FDA approved to reduce or control blood sugar in people diagnosed with Type 2 diabetes. Janumet combines two antidiabetic agents, metformin and sitagliptin. It is typically prescribed to patients already taking metformin or sitagliptin and not achieving sufficient blood glucose control. The recommended starting dose is lower for people who are not currently taking metformin or taking a lower dose of metformin.

In clinical trials, the combination of metformin and sitagliptin reduced A1C 2.1% in six months at the dose of 100 mg sitagliptin/2000 mg metformin per day. However, because sitagliptin mostly affects blood sugar after a meal, metformin-sitagliptin treatment is less likely to cause low blood sugar than other drug combinations with metformin. 

Metformin belongs to a family of drugs called biguanides and is often the first drug prescribed to control blood glucose levels. It works by increasing insulin sensitivity and decreasing both the amount of sugar absorbed in the digestive process and the amount of glucose manufactured in the liver. 

Sitagliptin belongs to a new family of antidiabetic drugs called dipeptidyl peptidase-4 inhibitors. DPP-4 is an enzyme that breaks down the hormones, called incretins, that promote the production of insulin. By blocking this enzyme, sitagliptin increases insulin production after a meal. Sitagliptin only affects insulin after a meal, reducing the risk of low blood sugar throughout the rest of the day.

• Standard dosage for Type 2 diabetes in adults: 50/500 or 50/1000 mg tablet taken twice per day

• Maximum dosage for Type 2 diabetes in adults: 100/2000 mg per day

Janumet dosage for children

Janumet has not been approved by the FDA for use in children. 

Janumet dosage restrictions

Janumet is a fixed-dose medicine, so dosage adjustments are not possible. For this reason, healthcare professionals are advised to avoid using Janumet in people with hepatic impairment (liver disease), moderate to severe renal impairment (eGFR < 45), or who are on dialysis.

Janumet cannot be given to people with certain pre-existing conditions. Called contraindications, these include allergic reactions to Janumet or its individual components, Type 1 diabetes, diabetic ketoacidosis, metabolic acidosis, lactic acidosis, dehydration, or anytime fluids are restricted, such as right before surgery. Some conditions may up the risk for side effects, but in certain cases, people with those conditions can still take Janumet with careful monitoring. These include congestive heart failure, low oxygen levels, excessive alcohol intake, swollen pancreas (pancreatitis), or people with risk factors for heart failure.

How to take Janumet

Each Janumet tablet has one dose of metformin and one dose of sitagliptin. A tablet is taken twice per day with food. 

• Follow the instructions given by a healthcare provider on how much Janumet to take and when. 

• Janumet is always packaged with a medication guide. Please read this guide every time a prescription is filled. It contains valuable information about how to take Janumet and what problems to watch out for.

• Swallow Janumet tablets whole. Do not break, cut, or chew them.

• Follow all the doctor’s recommendations on diet and exercise while taking Janumet.

• Regularly check blood sugar levels as instructed by a healthcare professional.

• Store Janumet at room temperature (68°F to 77°F) out of the reach of children and pets.

There may be times when Janumet should be stopped or the treatment changed. Tell the prescribing healthcare provider if

• You become dehydrated

• Have upcoming surgery

• Have any upcoming medical imaging procedures involving dyes or contrast agents 

• Have an infection, injury, or fever

Janumet dosage FAQs

Janumet vs. Janumet XR: What’s the difference in doses?

Janumet XR combines immediate-release sitagliptin with extended-release metformin to allow for a single daily dose. Janumet XR, however, comes in three dose strengths: 50 mg sitagliptin/500 mg metformin, 50 mg sitagliptin/1000 mg metformin, and 100 mg sitagliptin/1000 mg metformin.

How long does it take Janumet to work?

Janumet may start lowering blood sugar within a few days or weeks. However, clinical studies looked at the results after 24 weeks. People on the highest Janumet dose should see a decline of two percent by six months, while people on the lower dose should see a decline of about 1.6%.

How long does Janumet stay in your system?

Janumet combines two drugs. Each is eliminated at a different rate. The terminal half-life of metformin is 20 hours while half a dose of sitagliptin is eliminated in about 12.5 hours. That means it will take several days for the body to completely eliminate an entire single dose of Janumet. 

What happens if I miss a dose of Janumet?

Take a missed dose as soon as it’s remembered. If it’s almost time for the next dose, however, skip the missed dose and take the next dose on time. Never take two doses to make up for a missed dose.

How long can you take Janumet?

Janumet is intended for the long-term treatment of Type 2 diabetes. It can be taken for as long as the drug controls blood sugar and side effects are tolerable. There are situations, however, that will require the drug to be stopped at least temporarily. These include surgery that requires any fluid restrictions, iodinated contrast imaging procedures, dehydration, and trauma.

How do I stop taking Janumet?

Do not stop taking Janumet except under the direction of a healthcare professional. The sudden discontinuation of antidiabetic agents can cause blood glucose levels to rise unless other antidiabetic drugs are prescribed. Other than that, Janumet can be stopped at any time without causing withdrawal or other problems. 

A healthcare provider may stop Janumet treatment for many reasons including uncontrolled blood sugar, hypersensitivity reactions such as swelling (angioedema) or blistering skin (bullous pemphigoid), or serious adverse reactions such as heart failure, kidney failure (acute renal failure), swelling of the pancreas (acute pancreatitis), or severe joint pain (arthralgia). Some people may want to stop taking Janumet because of common side effects such as gastrointestinal problems, upper respiratory tract infection, or vitamin B12 deficiency. Talk to a healthcare provider about other options if side effects are hard to take.

For people who cannot take sitagliptin, a healthcare provider could prescribe another DPP-4 inhibitor or turn to other types of diabetic medications including sulfonylureas, meglitinides, alpha-glucosidase inhibitors, incretin mimetics, thiazolidinediones (glitazones), or insulin. These can be prescribed as monotherapy or in combination with other drugs.

If metformin is a problem, sitagliptin alone, sold under the brand name Januvia, is commonly combined with other medications including pioglitazone, rosiglitazone, glimepiride, or insulin. Merck also offers another combination antidiabetic drug under the brand name Steglujan, a combination of sitagliptin and ertugliflozin. 

What is the maximum dosage for Janumet?

The maximum daily dosage of Janumet is 100 mg of sitagliptin and 2000 mg of metformin, or two high-dose tablets.

Can you overdose on Janumet?

If too much Janumet is taken, call a poison helpline or get immediate medical help. An overdose may cause low blood sugar or lactic acidosis. People with Type 2 diabetes should be familiar with the signs of low blood sugar such as weakness, confusion, sweating, drowsiness, dizziness, fast heartbeat, and confusion. Treat these symptoms as instructed by a healthcare provider. Lactic acidosis is characterized by symptoms such as abdominal pain, diarrhea, fast and shallow breathing, muscle pain, cramping, weakness, and unusual fatigue. Lactic acidosis is a medical emergency, so always get immediate medical attention.

What interacts with Janumet?

Like all drugs, Janumet can cause problems when taken with other drugs. Always keep a list of all the drugs being taken to share with healthcare providers when getting prescriptions. This list should include prescription drugs, over-the-counter medications, and even dietary supplements and herbal remedies. 

Janumet’s most significant drug interactions involve other diabetes medications. In particular, the concomitant use of other DPP-4 inhibitors like sitagliptin is avoided in people taking Janumet. Co-administration of insulin secretagogues, that is, drugs that increase insulin secretion such as glyburide or glipizide, also significantly increases the risk of hypoglycemia. Alcohol can also increase the risk for low blood sugar, when combined with Janumet.

Most of the other drug interactions are with the metformin component in Janumet. One of the most serious side effects of metformin is lactic acidosis. There is an increased risk of lactic acidosis when Janumet is combined with alcohol, the stomach acid reducer cimetidine, or drugs called carbonic anhydrase inhibitors such as topiramate, a drug used to treat seizures or prevent migraines.

What happens when you mix Janumet and alcohol?

Avoid drinking alcohol when taking Janumet. In general, it’s not a good idea to drink alcohol when being treated for diabetes. However, combining metformin, one of the active ingredients in Janumet, with alcohol, can cause lactic acidosis, a potentially life-threatening side effect of metformin. Combining Janumet with alcohol can also cause low blood sugar.

Is it safe to take Janumet during pregnancy?

It is uncertain if Janumet can cause problems during pregnancy or harm a fetus. However, uncontrolled blood sugar can harm both the mother and the unborn baby. Pregnant women will need to consult with their healthcare provider about the best antidiabetic drug to take while pregnant. 

There are no studies of Janumet’s effects on lactation or a nursing baby. Healthcare professionals do not know if sitagliptin is present in human breast milk. However, metformin is present in human breast milk and has been detected in the blood of breastfed babies, although there is no evidence that it harms these babies. Mothers should consult with their healthcare provider about breastfeeding while taking Janumet. The healthcare provider may suggest alternative diabetes treatments.

Related resources for Janumet dosages:

• Adult diabetic ketoacidosis, StatPearls

• Janumet, Epocrates

• Janumet HCP, Merck

• Janumet prescribing information, U.S. National Library of Medicine

• Janumet XR prescribing information, U.S. National Library of Medicine

• Janumet, Merck

• Lactic acid, University of Michigan Health

• Metformin, StatPearls