There is no single “best” insulin for type 1 diabetes. The best regimen is a combination of two types: a long-acting (basal) insulin that works in the background all day and a rapid-acting (bolus) insulin you take at meals. What varies is which specific insulins within those categories work best for your body, your schedule, and your delivery method. The current standard of care pairs a long-acting insulin analog with a rapid-acting or ultra-rapid-acting insulin analog, delivered either through multiple daily injections or an insulin pump.
How Basal and Bolus Insulins Work Together
Your pancreas would normally release a small, steady stream of insulin around the clock, plus larger bursts when you eat. Type 1 diabetes treatment mimics this with two insulins. The basal insulin covers the steady background need, keeping blood sugar stable between meals and overnight. The bolus insulin handles the spike from food. You’ll take basal insulin once (sometimes twice) daily and bolus insulin before each meal. Getting the right pair, and the right doses of each, is what drives good blood sugar control.
Comparing Long-Acting Basal Insulins
Three basal insulins dominate type 1 diabetes management, and the key differences come down to how long they last and how likely they are to cause low blood sugar overnight.
The original long-acting analog, insulin glargine 100 units/mL (sold as Lantus and biosimilar versions), lasts roughly 20 to 24 hours. It works well for many people, but its activity can tail off before the next dose, and some people experience more overnight lows during the first weeks of dose adjustment.
The newer generation offers meaningful improvements. Insulin glargine 300 units/mL (Toujeo) is a concentrated version that absorbs more slowly from under the skin, giving a flatter, more stable profile. In clinical trials, it caused significantly fewer nighttime lows than the original glargine, especially during the initial dose-adjustment period. Insulin degludec (Tresiba) lasts over 42 hours, which means its effect overlaps from dose to dose and creates a very even background level. The BEGIN trial program showed degludec also reduces nighttime lows compared to original glargine.
A real-world comparison (the RESTORE-1 study) found that switching from original glargine to either Toujeo or Tresiba produced similar improvements in blood sugar control, with meaningful reductions in both moderate and serious low blood sugar events. Toujeo had a slight edge in safety: there were no severe hypoglycemic events in the Toujeo group compared to seven in the degludec group over six months. Both are strong choices, and the practical difference for most people is small.
Rapid-Acting Insulins for Meals
Rapid-acting insulins are what you take before eating. The three standard options, insulin lispro (Humalog), insulin aspart (NovoLog), and insulin glulisine (Apidra), all start working within about 15 to 30 minutes, peak at 1 to 3 hours, and last 3 to 5 hours. For most people, these are clinically interchangeable, and the choice often comes down to insurance coverage or personal preference.
Ultra-rapid-acting insulins are a newer step. Faster-acting insulin aspart (Fiasp) begins working in about 5 minutes and peaks at roughly 30 minutes. Ultra-rapid lispro (Lyumjev) has a similarly accelerated profile. The appeal is obvious: faster insulin means you can dose closer to the start of a meal (or even slightly after) and still catch the blood sugar rise. In injection studies, both reduce post-meal spikes compared to their conventional counterparts.
The tradeoff is that some people report more injection-site irritation with ultra-rapid formulations. And while faster onset sounds universally better, the advantage shrinks when these insulins are used inside an insulin pump’s automated system, as explained below.
Insulin Pumps and Automated Delivery
Automated insulin delivery (AID) systems, sometimes called hybrid closed-loop systems, pair an insulin pump with a continuous glucose monitor and an algorithm that adjusts basal insulin delivery automatically. The most widely used systems include the Tandem t:slim X2 with Control-IQ, the Omnipod 5, and Medtronic’s 780G. These systems use only rapid-acting insulin in the pump reservoir for both basal and bolus delivery.
You might expect ultra-rapid insulins to shine in pumps, since faster absorption should help the algorithm respond more quickly to rising blood sugar. In practice, the benefit has been modest. A randomized crossover trial using the Medtronic 670G found time-in-range of 78.4% with faster aspart versus 75.3% with standard aspart, a difference that’s small in daily life. A similar trial comparing ultra-rapid lispro to standard lispro on the same system showed virtually identical results (77.0% vs. 77.8%). Current AID algorithms were designed around the speed of conventional rapid-acting insulins, so ultra-rapid options don’t yet unlock a dramatic improvement.
If you’re using or considering an AID system, standard rapid-acting insulin (lispro or aspart) remains the most commonly used and well-tested option. Ultra-rapid insulins are worth discussing with your care team, but they aren’t a clear upgrade in this context yet.
Inhaled Insulin as a Bolus Option
Inhaled insulin (Afrezza) is the only non-injectable mealtime insulin available. It comes as a dry powder you breathe in through a small inhaler, and it reaches the bloodstream extremely fast, even quicker than ultra-rapid injected insulins. For people who struggle with multiple daily injections or needle fatigue, it’s an appealing alternative.
A 2024 randomized trial in Diabetes Care compared inhaled insulin plus basal injection against usual care (which included both AID systems and standard injection regimens). Inhaled insulin was statistically noninferior for A1c reduction. Among people previously on injections or non-automated pumps, 24% of those using inhaled insulin achieved time-in-range above 70% at 17 weeks, compared to 0% in the usual care group.
The results were more mixed overall. About 26% of participants on inhaled insulin saw their A1c worsen by more than 0.5 percentage points, compared to only 3% in the usual care group. This suggests inhaled insulin works very well for some people but requires careful dose titration. It also isn’t suitable for anyone with chronic lung disease, and periodic lung function testing is required.
Biosimilars and Cost Considerations
Insulin cost is a real factor in choosing a regimen. Biosimilar insulins are near-copies of brand-name biologics, approved by the FDA after demonstrating equivalent safety and effectiveness. Several biosimilars of insulin glargine (Lantus) and insulin lispro (Humalog) are now available and typically cost significantly less than their brand-name counterparts. Some carry an “interchangeable” designation, meaning a pharmacist can substitute them without needing a new prescription from your doctor, just like a generic drug.
If you’re paying out of pocket or facing high copays, switching to a biosimilar basal or bolus insulin can reduce your costs without sacrificing blood sugar control. The clinical performance is essentially identical to the reference product.
Once-Weekly Basal Insulin
Insulin icodec is a once-weekly basal insulin that completed phase 3 trials in type 1 diabetes (the ONWARDS 6 trial). It reduced A1c by 0.47 percentage points over 26 weeks, comparable to the 0.51 percentage points seen with daily degludec. However, the rate of clinically significant or severe low blood sugar was nearly double with the weekly insulin: 19.9 events per patient-year versus 10.4. Time spent with dangerously low blood sugar (below 54 mg/dL) was also significantly higher.
For type 1 diabetes specifically, this higher hypoglycemia risk is a serious limitation. Weekly dosing is convenient, but it also means you can’t easily fine-tune your background insulin from day to day, which matters when activity levels, stress, and illness cause your needs to shift. Icodec is not yet widely available for type 1 diabetes, and if it does become an option, it will likely be best suited for people who have very stable, predictable insulin needs.
Choosing What Works for You
The “best” insulin regimen depends on several practical realities: whether you use injections or a pump, how sensitive you are to low blood sugar, how variable your daily routine is, and what your insurance covers. A few principles hold true across the board. Newer-generation basal insulins (degludec or concentrated glargine) cause fewer overnight lows than original glargine. Standard rapid-acting insulins remain the workhorse for meal coverage, with ultra-rapid versions offering a modest speed advantage that matters more for injections than for pump use. AID systems, when accessible, consistently deliver the highest time-in-range results regardless of which rapid-acting insulin fills the reservoir.
Your insulin needs will also change over time. Honeymoon periods after diagnosis, puberty, pregnancy, shifts in weight or activity, and aging all alter how much insulin you need and how your body responds to it. The best regimen is one you revisit regularly with your care team, not one you set and forget.