Insulins are grouped by how fast they start, when they peak and how long they last: rapid-acting starts in minutes, long-acting lasts 16 to 42 hours. Here is how the classes compare, what U-100 to U-500 mean, what speeds or slows absorption, how insulin is stored and what biosimilars are.
There are five main kinds of insulin, grouped by how quickly they start working and how long they last: rapid-acting, short-acting (regular), intermediate-acting (NPH), long-acting, and premixed insulins that hold a fixed ratio of two insulins in one vial or cartridge 5. In Diabetes Canada’s guideline table, the fastest, faster-acting insulin aspart, starts working in about 4 minutes, and the longest, insulin degludec, lasts about 42 hours 5.
Those differences decide when an insulin can cover a meal, when its effect is strongest and how long it keeps working after its peak 5. Our article on insulin on board looks closely at that tail.
This article uses generic names first, with the brand names Canadian guidelines list. It is education only: which insulin you use, how much and when are decisions you make with your prescriber.
People with type 1 diabetes must take insulin because the pancreas no longer makes it, and many people with type 2 diabetes also need insulin 1, 2. Diabetes Canada calls insulin “the life-sustaining therapy for people living with type 1 diabetes” 3. How the two types differ is covered in type 1 vs type 2 diabetes.
In type 2 diabetes, Mayo Clinic notes that insulin is needed when healthy-lifestyle changes and other treatments don’t control blood sugar well enough 12. Diabetes Canada’s 2024 type 2 guideline says insulin needs will likely increase as diabetes progresses. It recommends starting insulin right away for people with metabolic decompensation or severe high blood sugar with symptoms, whatever their A1C 13.
The ADA’s 2026 Standards of Care say insulin replacement plans typically consist of basal insulin, mealtime insulin and correction insulin 4. Basal, or background, insulin covers your needs when you are not eating: in Mayo Clinic’s words, long-, ultralong- or intermediate-acting insulin “prevents blood sugar levels from rising without eating” 12. It can come from NPH, a long-acting analogue, or rapid-acting insulin delivered continuously by a pump 4.
Bolus insulin is a dose taken for food (mealtime) or to bring a high reading down (correction). Mayo Clinic describes rapid-acting insulins as “ideal for use before meals” 12. For most adults with type 1 diabetes, the ADA recommends a pump or multiple daily doses of mealtime and basal insulin 4. In type 2 diabetes, Diabetes Canada recommends one daily basal injection as the first insulin, with mealtime insulin added later if needed, starting at the largest meal 13.
In plain terms: Basal insulin is the slow, steady background that keeps glucose from drifting up when you are not eating. Bolus insulin is the quick dose for a meal or a high reading. People with type 1 diabetes need both. Many people with type 2 diabetes start with basal insulin alone.
The main difference between insulin types is timing: how soon each starts working (onset), when its effect is strongest (peak) and how long it lasts (duration) 5. NPH and premixed insulins look cloudy; the others are clear 5.
| Insulin (brand names in the table) | Onset | Peak | Duration |
|---|---|---|---|
| Rapid-acting: aspart (NovoRapid) | 9–20 min | 1–1.5 h | 3–5 h |
| Rapid-acting: glulisine (Apidra) | 10–15 min | 1–1.5 h | 3.5–5 h |
| Rapid-acting: lispro U-100, U-200 (Humalog) | 10–15 min | 1–2 h | 3–4.75 h |
| Rapid-acting: faster-acting aspart (Fiasp) | 4 min | 0.5–1.5 h | 3–5 h |
| Short-acting: regular (Humulin R, Novolin ge Toronto) | 30 min | 2–3 h | 6.5 h |
| Short-acting: regular U-500 (Entuzity) | 15 min | 4–8 h | 17–24 h |
| Intermediate-acting: NPH (Humulin N, Novolin ge NPH) | 1–3 h | 5–8 h | Up to 18 h |
| Long-acting: detemir (Levemir) | 90 min | Not applicable | 16–24 h |
| Long-acting: glargine U-100 (Lantus, Basaglar) | 90 min | Not applicable | 24 h |
| Long-acting: glargine U-300 (Toujeo) | 90 min | Not applicable | More than 30 h |
| Long-acting: degludec U-100, U-200 (Tresiba) | 90 min | Not applicable | 42 h |
The appendix gives no separate timings for premixed insulins 5. Other official sources can differ: the Health Canada–authorized product monograph for Novolin ge NPH gives a maximal effect at 4 to 12 hours and a duration of about 24 hours 14. Treat any single figure as typical, not a promise about your next dose.
The appendix dates from 2018. Diabetes Canada’s 2025 type 1 guideline adds that several biosimilar insulins are now available in Canada: insulin aspart (Kirsty, Trurapi), insulin lispro (Admelog) and insulin glargine 100 units/mL (Basaglar, Semglee) 3.
A biologic drug is made using biotechnology from living organisms or their cells. A biosimilar is produced after the patent on the original (reference) biologic expires, and it is similar to, but not identical to, the original, so it is not a “generic” 11. Similarity is shown in comparative studies, and once Health Canada authorizes a biosimilar it issues a Notice of Compliance and a Drug Identification Number (DIN) 11. Diabetes Canada’s position is that “the decision to use a biologic drug or a biosimilar insulin must be made jointly by patients living with diabetes and their health care providers” 11.
Rapid-acting insulin analogues start working sooner and wear off faster than short-acting (regular) human insulin 3. In the guideline table, rapid-acting analogues start in 9 to 20 minutes and last 3 to 5 hours, while regular insulin starts in about 30 minutes and lasts about 6.5 hours 5.
Analogues are lab-made versions of insulin designed to act faster or longer than human insulin. Faster-acting insulin aspart is the quickest in the table, starting in about 4 minutes 5. Diabetes Canada calls insulins like it ultrarapid analogues: taken before a meal, they reduce the rise in glucose after eating compared with rapid analogues, but this did not improve A1C except in one trial of children and adolescents 3.
For most adults with type 1 diabetes, the ADA prefers insulin analogues (or inhaled insulin) over injectable human insulins to minimize the risk of lows 4. Diabetes Canada’s type 2 guideline says rapid-acting analogues may be considered over regular insulin for the same reason 13. Our article on low blood sugar covers warning signs and treatment.
Intermediate-acting NPH insulin peaks 5 to 8 hours after injection and lasts up to 18 hours, while long-acting analogues have no peak and last 16 to 42 hours 5. Both serve as basal insulin 4.
NPH (neutral protamine Hagedorn) is a human insulin, and the ADA lists a higher risk of lows with human insulin, NPH or premixed, than with analogues 4. Diabetes Canada’s type 1 guideline reports that, in all ages, long-acting analogues improve A1C and reduce night-time lows compared with NPH, and in adults and older adolescents also reduce severe lows 3.
Among the long-acting analogues, Diabetes Canada calls glargine U-300 an ultralong analogue 3. Its type 2 guideline links degludec with fewer overall, symptomatic, night-time and severe lows than glargine U-100, finds some evidence of fewer lows with glargine U-300 than U-100, and rates glargine U-100 and detemir as similar 13. If waking readings run high, see the dawn phenomenon.
Insulin icodec (Awiqli) is a long-acting basal insulin taken once a week instead of once a day. Health Canada issued a Notice of Compliance for it on March 12, 2024, for the once-weekly treatment of adults with diabetes, and describes it as the first basal insulin given weekly rather than daily 15. It is concentrated at 700 units per mL 15. In the type 1 diabetes trial Health Canada reviewed, severe or clinically significant lows were more frequent with weekly icodec than with daily insulin degludec, about 1,841 versus 861 events per 100 patient-years, and the review concluded that it would be best suited to people with type 1 diabetes who have good awareness of their lows 15.
Premixed insulins hold a fixed ratio of insulin in a single vial or cartridge, written as the percentage of rapid- or short-acting insulin to the percentage of intermediate-acting insulin 5. Humulin 30/70 and Novolin ge 30/70, 40/60 and 50/50 mix regular insulin with NPH. The analogue premixes are biphasic insulin aspart (NovoMix 30) and insulin lispro with lispro protamine (Humalog Mix25 and Mix50) 5. Because the ratio is fixed, the mealtime and background parts cannot be changed separately.
The U number is the concentration, the number of insulin units in each millilitre: U-100 insulin has 100 units per mL, and U-200, U-300 and U-500 have 200, 300 and 500 units per mL 14, 3, 6, 7. The concentrated forms in Diabetes Canada’s table are lispro U-200 (Humalog), degludec U-200 (Tresiba), glargine U-300 (Toujeo) and regular U-500 (Entuzity) 5.
Concentration matters for two reasons. The first is volume: the same number of units fits into less liquid, and U-500 regular insulin is used for people who are highly insulin resistant 7. The second is timing. Diabetes Canada says degludec at 100 and 200 units/mL has similar pharmacokinetics and pharmacodynamics (how the body absorbs the insulin and how it acts), while glargine at 300 units/mL differs enough from 100 units/mL to make it an ultralong analogue 3.
In a laboratory (clamp) study of 30 people with type 1 diabetes, glargine U-300 gave a more even effect over 24 hours than glargine U-100 and kept glucose at or below 5.8 mmol/L (105 mg/dL) for about 5 hours longer, a median of 30 hours 6. In 24 healthy adults with obesity given single 50- or 100-unit doses, U-500 regular insulin delivered the same overall insulin and glucose-lowering effect as U-100 regular, but with a lower peak and a longer effect after it 7. At those large doses, both lasted 18.3 to 21.5 hours 7, far longer than the 6.5 hours the guideline table lists for U-100 regular insulin 5.
Most insulin is injected into the fat just below the skin with a pen or a needle and syringe, or delivered continuously by an insulin pump 12, 16. International recommendations from 183 diabetes experts in 54 countries say the shortest needles, currently 4-mm pen and 6-mm syringe needles, are safe, effective and less painful, and that injections into muscle should be avoided, especially with long-acting insulins, because severe lows may result 17.
A pump gives small, steady amounts of rapid-acting insulin through the day, working like a long-acting injection, plus bursts of insulin with food, through a thin tube under the skin 12. Diabetes Canada names automated insulin delivery (AID) systems, a pump linked to a continuous glucose monitor, as the preferred treatment for all people with type 1 diabetes who are willing and able to use them 3.
Inhaled insulin (Afrezza) is a rapid-acting insulin breathed in at the start of each meal 12. The ADA says it has a rapid peak and shorter action than rapid-acting analogues and “may be used in place of injectable prandial insulin in the U.S.” 4. NIDDK says it is only for adults 1, and Mayo Clinic says people who smoke, or who have lung problems such as asthma or chronic obstructive pulmonary disease, should not use it 12. It is not listed in Diabetes Canada’s insulin table 5.
The injection site, exercise of the injected area, heat and lumpy skin can all change how fast insulin reaches the blood, and heat, freezing and light can damage the insulin itself 14, 8, 9, 10.
Site. NIDDK says insulin works fastest when injected into the belly; the thigh, buttocks and upper arm are other sites 1. The Novolin ge monograph says absorption of that insulin is fastest from the abdomen and slowest from the thigh 14.
Exercise. In a 1978 study of people with insulin-dependent (type 1) diabetes, with insulin injected into the leg, an hour of on-and-off cycling increased the rate insulin left the injection site by 135% in the first 10 minutes, and it was still 50% higher after 60 minutes 8. Leg exercise had no such effect on arm injections. Compared with the leg, arm and abdominal injections reduced the glucose-lowering effect of the exercise by 57% and 89% 8. See also exercise and glucose.
Heat. In eight people with insulin-dependent diabetes, two 25-minute sauna sessions at 85°C sped insulin absorption by 110% compared with room temperature, and glucose afterward was 3.0 to 3.3 mmol/L (54.1 to 59.5 mg/dL) lower than on the control day 9.
Lumpy skin. Injecting in the same spot again and again can make the tissue harden 1; these fatty lumps are called lipohypertrophy. In 13 people with type 1 diabetes, insulin lispro injected into such tissue reached a lower peak (61 versus 79 mU/L), varied far more (a coefficient of variation of 52% versus 11%), and glucose two hours after a test meal was 8.3 versus 5.8 mmol/L (150 versus 104 mg/dL) 10. The injection recommendations say not to inject into these lesions and that correct site rotation helps prevent them 17.
Each product’s monograph sets its own limits. The Health Canada–authorized monograph for Novolin ge, for example, says insulin not in use belongs in a refrigerator at 2 to 10°C, not near the freezer section, and that frozen insulin must not be used 14. In use, it should not be refrigerated: a vial can be kept at room temperature, not above 25°C, for up to 4 weeks, and a cartridge in a pen, not above 30°C, for up to one month, protected from excessive heat and light 14. Johns Hopkins Medicine adds not to leave insulin in direct sunlight, in a car trunk or glove compartment, or directly on ice or a gel pack 18.
In Diabetes Canada’s guideline table, faster-acting insulin aspart (Fiasp) has the quickest onset, about 4 minutes, against 9 to 20 minutes for the other rapid-acting analogues 5. Diabetes Canada calls insulins like it ultrarapid analogues 3.
Basal insulin is background insulin that keeps glucose from rising when you are not eating, from NPH, a long-acting analogue or a pump 12, 4. Bolus insulin is a dose for a meal or to correct a high reading. Insulin replacement plans typically combine basal, mealtime and correction insulin 4.
It depends on the product, and each monograph sets its own limit. For Novolin ge, a vial in use can stay at room temperature, not above 25°C, for up to 4 weeks, and a cartridge in a pen, not above 30°C, for up to one month 14. Johns Hopkins Medicine notes that a bottle in use may be kept at room temperature for one month 18.
No. NPH is intermediate-acting: it starts in 1 to 3 hours, peaks at 5 to 8 hours and lasts up to 18 hours, while long-acting analogues have no peak 5. Diabetes Canada says long-acting analogues reduce the relative risk of symptomatic and night-time lows compared with NPH 13.
They are similar, but not identical, to the original insulin, so they are not generics 11. Their similarity is shown in comparative studies before Health Canada authorizes them, and Diabetes Canada says the choice to use one should be made jointly by the person and their care team 11.
Insulin timing is easier to understand next to your own glucose line. Glyve keeps glucose, food, insulin, exercise, sleep and stress on one timeline, so you can see how your readings moved in the hours after a mealtime dose, or what happened when a workout followed an injection. You can log by typing, by voice or with a photo of a meal, a nutrition label or a barcode, and every estimate is a draft you check before saving. The day view shows your glucose graph against the target range you set, and the week view shows whether a pattern repeats. Glucose comes from Apple Health, from Dexcom and FreeStyle Libre through your own Dexcom Share or LibreLinkUp follower account (readings can arrive later than in your CGM app), or from meter readings you type in. PDF, CSV and AGP exports let you share what you logged with your care team when you choose. Glyve is not a medical device: it gives no medical advice and recommends no insulin doses, so the type, timing and amount of your insulin stay decisions for you and your care team.
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Glyve keeps glucose, food, insulin, exercise, sleep and stress on one timeline.
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