Insulin degludec (Tresiba)

How Medicare covers it

Part D (insulin pens and vials used at home). Part A during a covered inpatient stay. Insulin used in a covered insulin pump follows the Part B pump route stated on the gated insulin packages; this package's figures are the Part D formulary aggregation.

What it treats

Diabetes mellitus in patients 1 year of age and older — to improve glycemic control (blood sugar control) in type 1 and type 2 diabetes. It is not recommended for the treatment of diabetic ketoacidosis.

What it is for, in depth

Tresiba (insulin degludec) is a once-a-day, long-acting basal insulin for people with diabetes whose bodies do not make enough insulin (type 1) or do not use it well enough (type 2). It supplies the steady background insulin the body needs around the clock to keep blood sugar from rising between meals and overnight. A doctor prescribes it for adults and for children 1 year of age and older; in type 1 diabetes it is always combined with a short-acting insulin taken at meals, while in type 2 diabetes it may be the first insulin added when pills alone no longer control blood sugar, with a usual starting dose of 10 units a day. Because one injection lasts at least 42 hours, adults can take it at any time of day, which makes the schedule more flexible than older basal insulins. It comes as FlexTouch pens and a vial: the U-100 pen delivers 1-unit steps up to 80 units per injection and the U-100 multiple-dose vial holds 1,000 units, and the stronger U-200 pen delivers 2-unit steps up to 160 units per injection for people who need large doses — the pen's dose window shows the units directly, so no conversion math is needed. Unused Tresiba is stored in the refrigerator, and an opened pen or vial can be used for 56 days (8 weeks).

How it works

Insulin degludec is a long-acting human insulin analog (a lab-made basal insulin). Like all insulin, it lowers blood glucose by helping skeletal muscle and fat take up glucose from the blood and by stopping the liver from making glucose; it also stops fat and protein breakdown and helps the body build protein. After injection under the skin it forms multi-hexamers that create a depot (a slow-release store), so it is absorbed slowly and also binds to albumin in the blood. Its glucose-lowering effect lasts at least 42 hours, with a half-life of about 25 hours.

How it is taken

Injection under the skin (subcutaneous) of the thigh, upper arm, or abdomen, once a day — in adults at any time of day, in children at the same time every day. Rotate injection sites within the same area and do not inject into areas of lipodystrophy or localized cutaneous amyloidosis. Never give it into a vein or in an insulin pump, and never dilute or mix it with any other insulin. Do not transfer Tresiba from a FlexTouch pen into a syringe. The dose is individualized by diabetes type, metabolic needs, blood glucose results, and control goal, with increases usually every 3 to 4 days. Insulin-naive patients with type 1 diabetes usually start at about one-third to one-half of the total daily insulin dose (the rest is short-acting insulin at meals; Tresiba must be used with short-acting insulin in type 1 diabetes), and insulin-naive patients with type 2 diabetes start at 10 units once daily. Adults who miss a dose inject it during waking hours when remembered, keeping at least 8 hours between injections; children who miss a dose should contact their provider. Children needing less than 5 units a day use the U-100 vial.

Common side effects

Hypoglycemia (low blood sugar) is the most common adverse reaction with Tresiba, as with all insulins. Other reactions commonly associated with Tresiba are allergic reactions, injection site reactions, lipodystrophy (changes in the fat under the skin at injection sites), itching (pruritus), rash, edema (swelling from fluid), and weight gain. In trials, reactions in 5% or more of adults were nasopharyngitis (stuffy/runny nose and sore throat, 23.9% in type 1 and 12.9% in type 2 diabetes), upper respiratory tract infection (11.9% and 8.4%), headache (11.8% and 8.8%), sinusitis (5.1% in type 1), gastroenteritis (5.1% in type 1), and diarrhea (6.3% in type 2). Localized cutaneous amyloidosis at the injection site has been reported after approval.

Serious warnings

Severe hypoglycemia can cause seizures, can be life-threatening, and can cause death, and it can impair concentration and reaction time, which is dangerous when driving or operating machinery; the long action of Tresiba may delay recovery from hypoglycemia. Risk is higher with changes in dose, meal pattern, or physical activity, with other glucose-lowering drugs, and in patients with kidney or liver impairment or reduced awareness of hypoglycemia. Never share a Tresiba FlexTouch pen, needle, or syringe between patients, even if the needle is changed, because of the risk of blood-borne infections. Changes in insulin strength, maker, type, injection site, or method can cause high or low blood sugar and must be made under close medical supervision with more frequent glucose checks. Accidental mix-ups between insulin products can cause dosing errors and severe hypoglycemia — always check the label, and never use a syringe to draw Tresiba out of a pen. Severe, life-threatening generalized allergy, including anaphylaxis, can occur. All insulins can shift potassium into cells and cause hypokalemia, which untreated can cause respiratory paralysis, ventricular arrhythmia, and death. Used with thiazolidinediones (TZDs), it can cause fluid retention and new or worsening heart failure.

Who should be careful

Tresiba is contraindicated during episodes of hypoglycemia and in patients with hypersensitivity to insulin degludec or any of its ingredients. Extra care, closer glucose monitoring, and individual dose adjustment are needed in patients with kidney impairment or liver impairment, in patients with longstanding diabetes, diabetic neuropathy, or recurrent hypoglycemia who may not feel low blood sugar coming on, in patients whose meals, activity, or other medicines change, and during acute illness. Patients with visual impairment who rely on audible clicks to dial a dose should use FlexTouch pens with caution. Patients and caregivers must be taught to recognize and manage hypoglycemia, and self-monitoring of blood glucose is essential.

Major interactions

Many drugs raise the risk of hypoglycemia when used with Tresiba and may require a lower insulin dose and more glucose monitoring: other antidiabetic agents, ACE inhibitors, angiotensin II receptor blockers, disopyramide, fibrates, fluoxetine, monoamine oxidase inhibitors, pentoxifylline, pramlintide, salicylates, somatostatin analogs (such as octreotide), sulfonamide antibiotics, GLP-1 receptor agonists, DPP-4 inhibitors, and SGLT-2 inhibitors. Other drugs reduce insulin's glucose-lowering effect and may require a higher dose: atypical antipsychotics (such as olanzapine and clozapine), corticosteroids, danazol, diuretics, estrogens, glucagon, isoniazid, niacin, oral contraceptives, phenothiazines, progestogens, protease inhibitors, somatropin, sympathomimetic agents (such as albuterol, epinephrine, terbutaline), and thyroid hormones. Alcohol, beta-blockers, clonidine, and lithium salts can increase or decrease the effect, and pentamidine may cause hypoglycemia sometimes followed by hyperglycemia. Beta-blockers, clonidine, guanethidine, and reserpine can blunt the warning signs and symptoms of hypoglycemia, so more frequent glucose monitoring may be needed.

Cost and saving notes

If this drug is covered under your Medicare Part D plan and the cost is high, you can ask your plan for a tier exception to pay a lower cost share. If you have limited income, Extra Help (the Part D Low-Income Subsidy) can lower your Part D premiums and drug costs. In 2027, your total yearly out-of-pocket spending on covered Part D drugs is capped at $2,400, and you can spread those costs out in monthly payments through the Medicare Prescription Payment Plan. Ask your pharmacist and plan what you would pay before you fill, and check whether a generic or a different drug in the same class is on a lower tier. Under Medicare Part D, your share for a month's supply of covered insulin is capped at $35, and the Part D deductible does not apply to covered insulin.

Why it is in its tier

Insulin degludec (Tresiba) sits on Tier 3 in 93.97% of the plans that list it (1512 of 1609 listing plans). Tier 3 is the preferred brand tier — mid-level copays or coinsurance. The data-visible drivers: It is a brand-only product with no generic version in the formulary data, and the CMS dashboard puts its average Part D spending at about $2,435 per beneficiary for 2024 — a mid-cost drug, which matches where plans place it. Only 29.28% of Part D plans list it at all, so many readers will find their plan does not list it and covers a similar drug instead. The tier shown is the most common one; individual plans vary.

Sources

• TRESIBA (INSULIN DEGLUDEC) INJECTION, SOLUTION [NOVO NORDISK] — DailyMed
• MedlinePlus — National Library of Medicine
• MedlinePlus — Insulin Degludec

What official patient guides say

Insulin degludec comes as a solution (liquid) in vials and in prefilled dosing pens, to inject under the skin once a day at the same time every day. You or a caregiver will be shown how to inject it before the first dose, and you should read the instructions for use carefully. Inject it in the upper arm, thigh, or stomach area, never into a vein or muscle, and change the injection site within the chosen area with each dose, trying not to use the same site more often than once every 1 to 2 weeks. Always check that it looks clear and colorless before injecting, never reuse needles or pens, remove a pen needle right after the dose, and do not dilute, mix, or use it in a pump. If you miss a dose, inject it as soon as you remember, unless it is less than 8 hours before the next dose, in which case skip it and do not take a double dose. Store unopened pens and vials in the refrigerator and never let them freeze.

Source: MedlinePlus — Insulin Degludec

Part D formulary coverage

Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.

What you pay

Without insurance, the cash benchmark is 9.02222 per unit (TRESIBA 100 UNIT/ML VIAL) — about nan for 30 units. NADAC benchmark — the average price pharmacies pay (CMS, as of 2026-11-04). Pharmacy shelf prices vary.

A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.

Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-08

Coverage by plan and tier

Of the 5,495 Medicare drug plans we track for 2027, 1,609 list Insulin degludec (Tresiba) — 29.3% of plans. Most of those plans put it on Tier 3: 1,512 plans, 94.0% of the plans that list it. Other plans place it on Tier 1 (64 plans), Tier 4 (31 plans) or Tier 6 (2 plans). For example: Humana Total Complete (HMO) puts it on Tier 3; Humana Dual Integrated (HMO D-SNP) puts it on Tier 3; Humana Total Complete (HMO-POS) puts it on Tier 3. You can compare these plans side by side on our Medicare Advantage hub. A tier is not a price. What you pay also depends on whether you have met your plan';s deductible, whether the drug costs a flat copay or a share of the price, and whether you get Extra Help or Medicaid.

Read next

• Part D in 2027: The $700 Deductible, the $2,400 Cap, and the $35 Insulin Rule
• Extra Help in 2027: Lower Drug Copays and Who Qualifies
• Checking Medicare Savings Programs and Extra Help

Part D spending averages (2024)

Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30

Companies covering this drug

Part D and Medicare Advantage plan sponsors that list this drug on a formulary, 50 at a time.