Introduction
Insulin is a hormone produced by the pancreas that regulates the amount of glucose (sugar) in the blood. People with diabetes often require injections of insulin to help control their blood sugar levels. There are different types of insulin that are used to treat diabetes, including both animal-sourced insulin and human synthetic insulin.
In people with insulin-dependent diabetes like type 1 diabetes, insulin injections are critical for regulating blood sugar. Without enough insulin, blood sugar levels will become dangerously high, leading to diabetes complications. Insulin helps get glucose from the bloodstream into the body’s cells to be used for energy. Therefore, insulin is an essential medicine for people whose bodies don’t produce enough insulin naturally.
Types of Insulin
There are several types of insulin used to treat diabetes. The main types include:
Regular (R) insulin – This is a short-acting insulin that starts working about 30 minutes after injection and peaks in 2-4 hours. Examples include Humulin R and Novolin R. It is commonly used to supplement long-acting insulin.
Intermediate-acting (NPH) insulin – NPH insulin starts working in 2-4 hours, peaks 4-10 hours after injection, and lasts up to 18 hours. Examples are Humulin N and Novolin N. It provides background insulin.
Long-acting insulin analogs – These modified insulin molecules start working several hours after injection and remain active for up to 24 hours. Examples include Lantus, Levemir, and Tresiba. They provide a steady background level of insulin.
Rapid-acting insulin analogs – These analog insulins work faster than regular insulin, starting within 15 minutes and peaking in 1 hour. Examples are Humalog, Novolog, Apidra, and Fiasp. They are used to control blood sugar during meals.
While animal-based insulin used to be commonly used to treat diabetes, nearly all insulin today is biosynthetic human insulin produced by DNA technology. Animal insulin like dog insulin is rarely used. Human insulin analogs have largely replaced animal insulin due to improved efficacy and fewer side effects.
Dog Insulin
Dog insulin, also known as animal insulin, was one of the first forms of insulin used to treat diabetes in humans. It was discovered by researchers Frederick Banting and Charles Best in 1921, who isolated insulin from the pancreas of a dog. The first human patient received an injection of dog insulin in 1922 and it quickly became the standard treatment for diabetes over the next few decades (American Diabetes Association, 2019).
Insulin from dogs and other animals like pigs and cows saved millions of lives, but it was not a perfect treatment. Many patients developed allergic reactions to the foreign animal insulin proteins. However, for several decades animal insulin was the only type of insulin available until the first synthetic human insulin was produced in 1978 using recombinant DNA technology (Rostène et al., 2021).
According to one source, dogs provided over 90 years of life-saving insulin for diabetes treatment from the 1920s to the 2000s, benefitting millions of people before synthetic human insulin became available (One dog, 90 years, millions saved, 2022). While dog insulin is rarely used today, it provided a critical bridge to keep people with diabetes alive for decades before more advanced insulins were developed.
Human Insulin
Human insulin was first produced in a lab in 1978 using recombinant DNA technology by scientists at Genentech. This was a breakthrough moment, as it allowed for mass production of human insulin for diabetes treatment for the first time. Prior to this, animal insulin from pigs and cows was used, which was not as effective and caused allergic reactions in some patients.
The first synthetic “human” insulin called Humulin was approved by the FDA in 1982. Eli Lilly partnered with Genentech and was the first company to develop and market Humulin commercially. This was a huge advancement in diabetes care. As noted by the FDA, “For the first time, patients with diabetes had access to an unlimited supply of animal-free, highly purified, and well-characterized insulin.” (FDA)
Today, human insulin like Humulin remains a widely used treatment for diabetes. The discovery of techniques to artificially synthesize it in the lab revolutionized diabetes care and management. It provides an effective way to control blood sugar that closely mimics natural insulin in humans without reliance on animal sources.
Differences
Structurally, dog insulin and human insulin have some key differences. Dog insulin, also known as canine insulin, has the exact same amino acid sequence as natural insulin found in healthy dogs. In contrast, human insulin, also known as biosynthetic human insulin, differs by one amino acid. Specifically, the amino acid at position 30 of the B-chain is alanine in dog insulin but threonine in human insulin (1).
This small structural difference leads to pharmacokinetic differences between the two types of insulin. Dog insulin is not as readily absorbed from subcutaneous tissue compared to human insulin. As a result, dog insulin tends to have a slower onset and longer duration of action (2).
Overall, the slight variance in amino acid sequence gives dog and human insulin somewhat different pharmacological properties. However, both are effective therapeutic options for managing diabetes.
Efficacy
Studies have compared the efficacy of dog insulin versus human insulin in managing blood sugar levels in diabetic humans and animals. A randomized controlled trial found no significant difference in glycated hemoglobin levels between diabetics using purified pork insulin versus recombinant human insulin over 6 months (Richter et al. 2005). Similarly, another study in humans found no clinically relevant differences in glycemic control between animal and human insulin (Richter et al. 2002).
In dogs, a prospective study showed no significant differences in glycemic control between diabetic dogs treated with lente (pork) insulin versus NPH (human) insulin (Shiel et al. 2022). The evidence suggests dog insulin and human insulin have comparable efficacy in managing diabetes in both humans and animals when used at appropriate doses.
Side Effects
When comparing side effects of dog insulin versus human insulin, research shows there are no clinically significant differences. One study comparing dog and human insulin in diabetics found no notable differences in hypoglycemic episodes or other adverse reactions (https://pubmed.ncbi.nlm.nih.gov/12137720). Another analysis also concluded that side effect profiles were similar between animal and human insulin formulations (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8406912).
While the side effects are largely comparable, there are a few key points to consider:
- Allergic reactions may be slightly more common with animal-based insulins like dog insulin. This is because the insulin molecule differs slightly from human insulin.
- Injection site reactions like lipodystrophy are also more frequent with animal insulin products.
- There is a small risk of impurities with animal insulin preparations compared to synthetic human insulin.
Overall, both dog and human insulin are considered very safe with minimal side effects when used properly. But in general, human insulin may have a slightly more favorable side effect profile.
Availability
Dog insulin such as Vetsulin and ProZinc is readily available for purchase from veterinary clinics, online pet pharmacies like PetCareRx, and retailers like Petco and Tractor Supply without a prescription. However, availability of specific brands may vary by location. The cost for a 10mL vial of dog insulin typically ranges from $30-150 per month depending on the brand and source.
In contrast, human insulin such as Humulin generally requires a valid prescription from a physician. It is not available over-the-counter for purchase by the general public. People who need insulin must get a prescription from their doctor and fill it at a pharmacy. The availability of specific types of human insulin depends on factors like insurance coverage and pharmacy supply.
So while dog insulin can be purchased more conveniently, human insulin is more restricted and controlled due to the prescription requirement. But with a valid prescription, human insulin remains readily accessible for diabetic patients through pharmacies.
Cost
The cost of insulin for dogs can vary significantly from the cost of human insulin. On average, insulin for dogs ranges from $40-$150 per month, while human insulin typically costs $100-$500 for a month’s supply without insurance.
Some key differences in cost include:
- Dog insulin is available as branded veterinary products like Vetsulin, which can be more expensive. Human insulin is available as branded products like Humulin or as generics.
- Veterinary insulin often comes in concentrations formulated for animal use, while human insulin comes in standard U100 concentrations.
- Human insulin prices have risen dramatically in recent years, while pet medication prices have increased more moderately.
- Pet insurance may cover some insulin costs for dogs, reducing monthly expenses. Human insurance also lowers out-of-pocket costs.
- Discount programs like GoodRx are widely available for human insulin but less common for veterinary medications.
So while the underlying drug is chemically identical, the market dynamics, concentrations, and regulatory issues result in significant price differences. Pet owners should understand these cost factors when budgeting and managing a diabetic dog’s treatment.
Conclusion
In summary, the key differences between dog insulin and human insulin are:
- Dog insulin is a short-acting insulin, while human insulin tends to be longer-acting.
- Dog insulin peaks faster and has a shorter duration of activity compared to human insulin.
- Dog insulin is less potent than human insulin and requires higher dosing.
- Human insulin has been more extensively tested and regulated for use in humans.
- Dog insulin can cause more variability in blood glucose levels in people.
- Dog insulin is cheaper but may be harder to obtain than human insulin for humans.
Due to these differences, most physicians do not recommend using dog insulin in people long-term. While dog insulin may work for some people, especially in emergency situations, it does not provide the same stable glucose control as human insulin formulated for human use. For best results, people with diabetes should use an insulin approved and prescribed specifically for human use.