Porcine Insulin Zinc Suspension
The intermediate-acting pork insulin that people once injected and diabetic dogs and cats still do
Porcine insulin zinc suspension is purified pork insulin held in a cloudy suspension with zinc, partly as shapeless particles and partly as crystals, so that it is absorbed slowly from under the skin. This 'lente' form was a human insulin in the 1980s and was studied in people then. Today it is sold as a veterinary medicine, Vetsulin in the US and Caninsulin in the UK, for diabetic dogs and cats. It comes at 40 units per mL, and its label warns that any syringe other than a U-40 syringe gives the wrong dose.
Used in human trials: 0.2 U/kg, Single dose, Subcutaneous injection (Study: healthy men, single-dose pharmacokinetics (Monotard MC)) Details ↓
Recommended Dosing
Used in human trials
No manufacturer dose exists for this use: these are amounts given in published trials, not recommendations.
What is it?
Before recombinant human insulin, people with diabetes injected insulin purified from pig and cattle pancreas, and the 1980s studies below compared pork insulins with the new human ones. Lente insulins are suspensions of insulin with zinc, part shapeless (amorphous) and part crystalline, made to act for most of a day. The veterinary product sold today, Vetsulin, holds 40 units of purified pork insulin per mL, 35% amorphous and 65% crystalline, according to its DailyMed veterinary label.
Three studies from the 1980s show how it behaved in people. In ten healthy men given a single injection, porcine insulin zinc suspension (the product Monotard MC) lowered blood sugar within three hours and kept it down for 24 hours, with a two-peaked insulin curve, much like a human crystalline zinc insulin. In six people with type 1 diabetes and high morning sugars, swapping porcine lente for human ultralente as the twice-daily background insulin lowered fasting glucose. And over three years, adults started on purified porcine lente made insulin antibodies, but fewer and later than those on beef insulin. Drugs@FDA lists no human pork lente product today.
In dogs, the same two-peaked pattern appears: insulin rises about three hours after the injection and again at about nine, and the effect lasts roughly 14 hours on average, from 10 to more than 24. A 60-day study of 53 diabetic dogs found blood sugar curves improved, thirst and urination fell in most, and two thirds needed injections twice a day; low blood sugar was the only important side effect. A 2021 study found its day-to-day glucose swings larger than those of the long-acting analogues glargine 300 and degludec when given twice daily.
In cats it acts faster and for a shorter time, peaking under two hours after injection and wearing off within about 12, which suits twice-daily dosing. In a 46-cat field study, most cats reached clinical stability and eight went into remission, but nine showed signs of low blood sugar, linked to higher doses. When cats whose lente insulin wore off too early were switched to a human protamine zinc insulin, their control and quality of life improved.
For a reader who keeps or buys insulin, the practical points come from the label. Vetsulin is for dogs and cats only and must be drawn with U-40 syringes or used in its own pen; it must not be given to an animal with low blood sugar or a known pork allergy. It is not a human medicine, and the old human studies give no basis for a person to use a veterinary product. Insulin overdose can cause dangerous hypoglycaemia in any species.
Mechanism of Action
It is insulin, acting on the insulin receptor to move glucose into cells. What sets it apart is the zinc suspension, which slows absorption from the injection site.
Two release rates
The suspension mixes amorphous and crystalline insulin (label); a two-peaked insulin curve followed injection in healthy men (1984 study) and in dogs, at about 3 and 9 hours (2009 study).
Lowers blood glucose
Blood glucose fell from about three hours after injection and stayed down for 24 hours in healthy men (1984 study).
Immune response
Purified pork lente provoked insulin antibodies, at lower levels and later than beef insulin, over three years in adults (1986 study).
Published Research
These studies were read from their PubMed abstracts on October 29, 2026: three in people from the 1980s, when pork lente was a human insulin, and nine in diabetic dogs and cats. Amounts in the dog and cat cards are veterinary amounts and are not human doses.
Single dose in ten healthy men
In a crossover study, fasting non-diabetic men received 0.2 U/kg of human crystalline zinc insulin or porcine insulin zinc suspension (Monotard MC). Both caused moderate hypoglycaemia within 3 hours that lasted 24 hours, with a two-peaked insulin curve. Glucose fell more slowly at 4 and 7 hours with the pork product, and its duration of action matched the human insulin.
Against human ultralente in type 1 diabetes
Six C-peptide-deficient patients with high fasting glucose tried twice-daily soluble insulin with either human ultralente or porcine lente in a randomised crossover. Glucose before breakfast averaged 7.2 mmol/l on ultralente against 12.0 on porcine lente; later in the day there was no difference.
Insulin antibodies over three years
Nine insulin-naive adults started on monocomponent porcine lente and nine on beef NPH insulin. Those on pork made significant antibodies, but at lower levels and later than those on beef, and antibody levels did not track how well diabetes was controlled.
Pharmacokinetics in ten diabetic dogs
Plasma insulin peaked at about 4 hours and, in eight dogs, again at about 11 hours, staying raised for 14 to 24 hours (mean 17.4). The authors judged the profile comparable to other intermediate-acting insulins used in dogs.
Efficacy and safety in 53 dogs
After a dose-finding period and 60 days of treatment, mean and nadir glucose on 12-hour curves were significantly lower; excess urination, thirst and ketones in urine fell in 82, 86 and 80% of dogs. Two thirds needed twice-daily injections, and hypoglycaemia was the only important adverse effect.
Two insulin peaks in eight dogs
In dogs with no insulin of their own, insulin peaked at about 3 and 9 hours after each injection and stayed above baseline for 15.5 hours on average. Glucose lowering began at about 3 hours, was lowest at about 8, and lasted a median of about 14 hours (10 to more than 24).
Day-to-day variability against newer insulins in dogs
In seven beagles with induced diabetes on continuous glucose monitors, twice-daily porcine lente had more day-to-day variability (coefficient of variation 42.6%) than glargine 300 or degludec (30.1 and 25.2%), with no difference in time spent below 70 mg/dL.
Pharmacology in 25 diabetic cats
Under the skin, Caninsulin reached peak plasma insulin at about 1.7 hours and lowest glucose at about 4.1 hours, with both back to baseline within 12 hours. The profile did not change after 5 or 9 weeks of treatment, and the authors judged it suitable for twice-daily use in cats.
Controlling diabetes in 25 cats for a year
Cats needed a median of 0.5 iu/kg twice a day, and only two needed more than 1.0 iu/kg. Their lowest glucose tended to be higher at night than by day. Seven went into remission, and control was good or excellent in the rest by the end.
What to measure in treated cats
Of the clinical and blood measures compared, water intake, maximum and mean glucose on a 24-hour curve and urine glucose best separated well-controlled from less well-controlled cats; blood lipids did not track control.
46 cats, prospective multicentre study
Starting at 0.25 to 0.5 IU/kg twice daily, 28 cats reached clinical stability and 8 went into remission. Signs of hypoglycaemia in nine cats were linked to doses of 3 units or 0.5 IU/kg or more, which the authors say calls for cautious, stepwise dose changes.
Switching cats to protamine zinc insulin
Twenty-two cats on porcine lente were moved to human recombinant protamine zinc insulin at the same dose. Fructosamine, insulin dose and clinical scores fell and quality of life improved; 5 went into remission. Six of 19 cats had a short action on porcine lente, and all six had longer action after switching.
Dosing Data
No human product of this insulin is marketed in the US today, and its label is for dogs and cats only. The one row below is the single amount given to healthy volunteers in a 1984 pharmacokinetic study, as stated in its abstract. The veterinary label doses are for pets and are not shown as doses.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
No product is approved for people. The approved veterinary product, as its US veterinary label describes it:
- Vetsulin (insulin pork injection) (veterinary): vetsulin ® is supplied as a sterile injectable suspension in multidose vials containing 10 mL of 40 International Units/mL porcine insulin zinc suspension or in multidose cartridges containing 2.7 mL of 40 International Units/mL porcine insulin zinc suspension. Vials are supplied in cartons of one, 10 mL vial.
Source: Vetsulin (insulin pork injection) veterinary label, How Supplied (DailyMed version 10, effective October 20, 2026).
Mixing a vial: a worked example
No worked example: none of the doses on this page is a fixed amount in mg or mcg injected under the skin or into a muscle (the routes given are: subcutaneous injection). There is no home-mixing step to show. The reconstitution calculator does the arithmetic for any vial.
Source: the route and amount of each dose row in Dosing Data below.
Storage before and after mixing
No product of Porcine Insulin Zinc Suspension is approved for people. The US veterinary label of the approved animal product says how it is stored:
Vetsulin (insulin pork injection) (veterinary): “Store in an upright position under refrigeration at 2°C to 8°C (36°F to 46°F).” “Do not freeze.” “Protect from light.” “The loaded VetPen ® can be stored on its side.” “Use contents within 42 days of first puncture.”
These describe the veterinary product in its own container, not a vial sold for people. The mixing guide sets out the general rules for a mixed vial, with their sources.
Source: Vetsulin (insulin pork injection) veterinary label, storage section (DailyMed version 10, effective October 20, 2026).
How it is taken
As it was given in human studies: Subcutaneous injection (Single dose; Study: healthy men, single-dose pharmacokinetics (Monotard MC)).
For injection technique, sites and needle disposal, see the mixing guide.
Source: Used in human trials: the route and frequency of each row in Dosing Data below.
What to expect, and when
How long it stays in the body: not established by a measurement cited on this entry.
How long the doses were given: Study: healthy men, single-dose pharmacokinetics (Monotard MC): One day, monitored for 24 hours.
When effects appear: unknown; no source on this page gives a time to effect for Porcine Insulin Zinc Suspension. Results reported in the studies are under Published Research.
Source: Used in human trials, the duration of each row in Dosing Data below.
Side effects, and when to stop or get help
From the Side Effects section: Hypoglycaemia: moderate low blood sugar lasting 24 hours after a single injection in healthy men (PMID 6242801); the main adverse effect in dogs (PMID 16231711) and in cats at higher doses (PMID 18619886); Insulin antibodies in most adults over three years, fewer than with beef insulin (PMID 3758926); Short duration of action in some cats (PMID 29172917); Larger day-to-day glucose swings than newer long-acting insulins in dogs (PMID 34241910). Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Porcine Insulin Zinc Suspension. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“From the human and animal studies and the veterinary label”).
Interactions
- medications given during the US clinical studies (antimicrobials, NSAIDs, thyroid and anti-thyroid drugs, diuretics, parasiticides, vaccines and others): no medication interactions were reported; the drug was not studied in dogs receiving corticosteroids
Every peptide's record, with its source: the interaction matrix.
Source: Vetsulin (porcine insulin zinc suspension), US FDA-approved veterinary label, Drug Interactions. DailyMed set 4472644f, version 10, effective October 20, 2026, read October 28, 2026.
Checking what you bought
Unknown: no published independent test of Porcine Insulin Zinc Suspension products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Veterinary Only (Approved only for animals in this form). Sport: Prohibited at all times (S4.4.2).
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
From the human and animal studies and the veterinary label.
Contraindications & Cautions
From the US veterinary label:
Legal Status
In this form it is approved only as a veterinary medicine.
Frequently Asked Questions
?What is porcine insulin zinc suspension?
Purified pork insulin suspended with zinc, partly amorphous and partly crystalline, so that it acts for most of a day. It is also called porcine lente insulin.
?Was it ever used in people?
Yes. In the 1980s purified pork lente, for example Monotard MC, was a human insulin, and studies compared it with human and beef insulins. Drugs@FDA lists no human pork lente product today.
?Who uses it now?
Diabetic dogs and cats, as Vetsulin in the US and Caninsulin in the UK, prescribed by a veterinarian.
?Why does the syringe matter?
Vetsulin is U-40, 40 units per mL, and its label warns that any syringe other than a U-40 syringe gives the wrong dose.
?Can a person use the veterinary product?
No. It is labelled for dogs and cats only; human insulin treatment is set by a doctor using human products.
References
- [fda-pi] Vetsulin (porcine insulin zinc suspension), US FDA-approved veterinary label (description, dosage and drug interactions; DailyMed set 4472644f, version 10, effective October 20, 2026; read October 28, 2026).
- [other] US FDA Center for Veterinary Medicine, Approved Animal Drug Products (Green Book), Section 2 active-ingredient list downloaded from Animal Drugs @ FDA, read October 28, 2026: NADA 141-236, Vetsulin, active ingredient porcine insulin zinc suspension. https://animaldrugsatfda.fda.gov/adafda/views/#/search
- [other] UK Veterinary Medicines Directorate, Product Information Database, currently authorised products searched by active substance, read October 28, 2026: Caninsulin 40 IU/ml suspension for injection, VM 06376/4083, active substance insulin, target species cats and dogs. https://www.vmd.defra.gov.uk/ProductInformationDatabase/
- [other] US FDA, Drugs@FDA (openFDA drugsfda endpoint): no application with brand name LENTE or active ingredient PORK. Searched October 29, 2026.
- [other] US FDA, Drugs@FDA (openFDA drugsfda endpoint): no application with brand name LENTE or active ingredient PORK. Searched October 29, 2026.
- [clinical-trial] Frier BM, et al. "Pharmacokinetics of human insulin zinc suspension (recombinant DNA) in normal man: a comparison with porcine insulin zinc suspension." Diabet Med, 1984;1(3):219-21. PMID: 6242801.
- [clinical-trial] Francis AJ, et al. "Human ultralente insulin: a comparison with porcine lente insulin as a twice-daily insulin in insulin-dependent diabetic patients with fasting hyperglycaemia." Diabetes Res, 1986;3(5):263-8. PMID: 3527523.
- [clinical-trial] Wajchenberg BL, et al. "Comparison of insulin antibody levels during the first 3 years of treatment of adult diabetics with monocomponent porcine lente-insulin and single peak beef NPH insulin." Horm Metab Res, 1986;18(8):535-9. PMID: 3758926.
- [pubmed] Graham PA, et al. "Pharmacokinetics of a porcine insulin zinc suspension in diabetic dogs." J Small Anim Pract, 1997;38(10):434-8. PMID: 9358402.
- [pubmed] Monroe WE, et al. "Efficacy and safety of a purified porcine insulin zinc suspension for managing diabetes mellitus in dogs." J Vet Intern Med, 2005;19(5):675-82. PMID: 16231711.
- [pubmed] Fleeman LM, et al. "Pharmacokinetics and pharmacodynamics of porcine insulin zinc suspension in eight diabetic dogs." Vet Rec, 2009;164(8):232-7. PMID: 19234324.
- [pubmed] Miller M, et al. "Day-to-day variability of porcine lente, insulin glargine 300 U/mL and insulin degludec in diabetic dogs." J Vet Intern Med, 2021;35(5):2131-2139. PMID: 34241910.
- [pubmed] Martin GJ, et al. "Pharmacology of a 40 IU/ml porcine lente insulin preparation in diabetic cats: findings during the first week and after 5 or 9 weeks of therapy." J Feline Med Surg, 2001;3(1):23-30. PMID: 11716627.
- [pubmed] Martin GJ, et al. "Control of diabetes mellitus in cats with porcine insulin zinc suspension." Vet Rec, 2007;161(3):88-94. PMID: 17652434.
- [pubmed] Martin GJ, et al. "Comparisons of different measurements for monitoring diabetic cats treated with porcine insulin zinc suspension." Vet Rec, 2007;161(2):52-8. PMID: 17630418.
- [pubmed] Michiels L, et al. "Treatment of 46 cats with porcine lente insulin--a prospective, multicentre study." J Feline Med Surg, 2008;10(5):439-51. PMID: 18619886.
- [pubmed] Gostelow R, et al. "Prospective evaluation of a protocol for transitioning porcine lente insulin-treated diabetic cats to human recombinant protamine zinc insulin." J Feline Med Surg, 2018;20(2):114-121. PMID: 29172917.
Sources & Citations
Every study on this page was read from its PubMed record on October 29, 2026. Label details come from the DailyMed veterinary label for Vetsulin (version 10, effective October 20, 2026), approval status from the FDA Green Book and the UK Veterinary Medicines Directorate (read October 28, 2026), and the human product check from Drugs@FDA (October 29, 2026). Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.