Alternatives to Tresiba if You Can't Fill Your Prescription

If you've been prescribed Tresiba (insulin degludec) and your pharmacy is out of stock, you may be wondering what your options are. First: don't panic — but don't skip your insulin either. Going without basal insulin can lead to dangerous blood sugar spikes, and for people with type 1 diabetes, it can cause diabetic ketoacidosis (DKA), a potentially life-threatening medical emergency.

The good news: there are several effective alternative basal insulins available. Your doctor can help you transition safely. Here's a detailed breakdown of each option, how it compares to Tresiba, and what you need to know about switching.

Important: Never Switch Insulins Without Your Doctor

Before we get into the alternatives, a critical point: do not switch basal insulins on your own. Each insulin has different onset times, peak activity, and durations of action. Dose conversions are not always 1:1. Your doctor needs to supervise any transition and may adjust your dose. Blood sugar should be monitored more frequently during the first 1-2 weeks after any switch.

Alternative 1: Insulin Glargine U-300 (Toujeo) — Closest Match to Tresiba

Toujeo is a concentrated formulation of Insulin Glargine (300 units/mL) that has a longer and flatter action profile than standard Insulin Glargine U-100 — lasting up to 36 hours. It's the closest match to Tresiba in terms of pharmacokinetics and is considered the best alternative if you value Tresiba's flat, ultra-long-acting profile.

Dose conversion: Switching from Tresiba to Toujeo may require a dose increase of 10-15%. Your doctor will help calculate the appropriate starting dose and titrate from there. Monitor blood sugar closely, especially in the first week.

Alternative 2: Insulin Glargine U-100 (Lantus, Basaglar, Rezvoglar) — Most Widely Available

Insulin Glargine U-100 is the most widely available and affordable long-acting basal insulin option. It's available as Lantus (brand), Basaglar (biosimilar), and Rezvoglar (biosimilar), among others. It has a duration of action of approximately 24 hours with a relatively flat profile — though not as flat as Tresiba.

Dose conversion: Switching from Tresiba to Insulin Glargine U-100 is typically a unit-for-unit conversion. However, some patients may need a dose reduction of about 20% to avoid hypoglycemia — your doctor will advise.

Cost advantage: Biosimilar glargine products like Basaglar and Rezvoglar are significantly less expensive than brand-name Tresiba. If cost has been a concern, this is worth discussing with your doctor.

Alternative 3: NPH Insulin — Emergency Option Only

NPH (Neutral Protamine Hagedorn) insulin is an intermediate-acting insulin that has been used for decades. It's not a true substitute for Tresiba — it has a pronounced peak (4-12 hours after injection), shorter duration (18-20 hours), and considerably more variability. However, it is available over the counter at some pharmacies without a prescription in some states, making it an option of last resort during a true emergency.

Important: NPH insulin is significantly different from Tresiba and typically requires twice-daily dosing. The increased peak activity raises the risk of hypoglycemia. Only use NPH as an emergency bridge — and do so under medical guidance if at all possible.

Comparing Tresiba vs. Alternatives at a Glance

Tresiba (insulin degludec): Duration 42+ hours, no peak, once daily, flexible timing, lowest nocturnal hypoglycemia risk.

Toujeo (insulin glargine U-300): Duration up to 36 hours, very flat profile, once daily — closest pharmacokinetic match.

Lantus/Basaglar (insulin glargine U-100): Duration ~24 hours, relatively flat, once daily, most widely available and affordable.

NPH Insulin: Duration 18-20 hours, pronounced peak, often twice daily — emergency use only.

Critical Tips for Switching Basal Insulins

Monitor blood sugar more frequently — especially at night — during the first 1-2 weeks of any switch.

Keep a log of your blood sugar readings and share it with your doctor during the transition period.

Watch for hypoglycemia at night — different insulins have different peak times, and the risk pattern may shift.

If you start an alternative insulin and Tresiba becomes available again, work with your doctor before switching back.

Before You Switch: Try Harder to Find Tresiba

Before switching insulins, make sure you've exhausted your options for finding Tresiba. Use medfinder to check multiple pharmacies at once — including independent pharmacies and mail-order options. Try both concentrations (U-100 and U-200). Expand your search radius to pharmacies 15-20 miles away.

See our complete guide: How to Find Tresiba in Stock Near You (Tools + Tips).