Insulin’s patent sold for $1, and then came the fights over price and carbs

Key takeaways

• On January 1, 1923, three of insulin’s discoverers handed the patent to the University of Toronto for one dollar, to keep anyone from locking up the method for private gain¹².
• In a 2015 NIH study, cutting carbs lowered insulin output, yet volunteers lost less body fat than when they cut the same calories from fat⁵.
• When researchers ran the same blood samples through 12 commercial insulin tests in 2025, only one fully agreed with a reference method⁸.
• Medicare has capped insulin at $35 a month per product since 2023, and in 2026 its negotiated price for NovoLog and Fiasp is $119 for a 30-day supply, 76% below the 2023 list price¹²¹³¹⁵.
• If you use insulin or a sulfonylurea pill, eating fewer carbs or exercising more can cause dangerous lows, so plan any change with your prescriber¹⁴.

In January 1922, a 14-year-old named Leonard Thompson lay gravely ill with diabetes at Toronto General Hospital. On January 11, doctors injected him with an extract made from animal pancreases¹.

It barely helped, and he had an allergic reaction¹. James Collip, a member of the research team, went back to the lab and refined the extract. On January 23, a second injection brought Thompson’s blood sugar down and cleared ketones, a sign of dangerous fat breakdown, from his urine¹.

The Toronto team chose not to cash in. On January 1, 1923, Frederick Banting, Charles Best and Collip signed their patent over to the university’s governing board for the sum of one dollar². An Ohio State University history essay calls it a sale for a token payment¹.

The point, the team wrote, was to stop outsiders from patenting the process themselves². Banting and John Macleod won the Nobel Prize that same year¹.

A century later, insulin sits at the center of two fights. One is over what it costs. The other is over diet, where “insulin makes you fat” became a slogan.

This article covers what insulin does every time you eat, what the research on weight has and hasn’t shown, and how to keep this old medicine affordable.

Insulin works within minutes, and it has a partner

Insulin comes from beta cells in your pancreas. When blood sugar rises after a meal, insulin signals your cells to pull sugar out of the blood³.

The liver gets one of the fastest messages. Between meals, the liver releases sugar to keep your blood supplied, and insulin tells it to stop⁴.

How fast? In a 1989 lab study, researchers Luzi and DeFronzo controlled the insulin release of six healthy volunteers⁴. With a normal insulin response, the liver’s sugar output fell 90% within 20 minutes⁴.

When the researchers blocked only the first quick burst of insulin, the liver’s output fell by about half after an hour and still wasn’t fully shut off at two and a half hours⁴. Losing that early burst may help explain why blood sugar starts creeping up early in diabetes, the authors suggested⁴.

Insulin has a counterweight. Alpha cells in the same pancreas make glucagon, which tells the liver to release sugar when blood levels drop³. The two hormones rein each other in, keeping blood sugar in a narrow band³.

Does insulin make you fat? Two camps, one stubborn question

Insulin does affect how your body handles fat. When carbs and insulin fall, the body burns more fat⁵. That’s the logic behind the popular idea that cutting carbs, and so cutting insulin, is a better path to fat loss.

The formal version is called the carbohydrate–insulin model. Among its leading supporters is David Ludwig, a co-author of the 2024 reanalysis described below⁶. Our low-carb article lays out the model and a disputed 2018 trial at Framingham State University. Here we look at the ward studies that challenge it.

There’s a real kernel here: insulin given as a medicine can cause weight gain, a side effect NIDDK tells patients to ask about⁹. Whether the insulin your own body makes after a bowl of rice drives obesity is a different question.

The tightly controlled test

In 2015, Kevin Hall’s team at the National Institutes of Health (NIH) moved 19 adults with obesity into a metabolic ward, a hospital unit where all food is measured⁵. Each person ate two reduced diets, one after the other, each cutting calories by 30%, from 2,740 to 1,918 a day, for six days⁵.

On the low-carb diet, 29% of calories came from carbohydrate. Daily insulin output fell, and the body burned more fat, just as the model predicts⁵.

Yet the low-fat diet, with under 8% of calories from fat, shed more body fat: about 89 grams a day, compared with 53 grams on the low-carb diet⁵. By our math, that gap adds up to roughly half a pound of fat over six days.

The study was small and short, and commentators noted it pooled men and women⁵. Still, it directly tested whether lowering insulin, with calories held equal, speeds fat loss. In the short run, it didn’t.

The fight over a later trial

In a later NIH ward study published in Nature Medicine, Hall’s team compared a plant-based, low-fat diet with an animal-based ketogenic diet, two weeks on each⁶⁷; our keto article describes it. People ate less on the low-fat diet even though it raised their insulin more, Hall’s group reported⁷.

In 2024, Ludwig and colleagues reanalyzed that trial in the Journal of Nutrition⁶. They found that the order of the diets mattered: how people ate on each diet depended on which one came first⁶. Two-week trials can’t capture how the body adapts to a new diet, they argued, and the data “tend to support” their model⁶.

Hall’s team, defending its own trial, answered in the same journal. They said the reanalysis skipped the trial’s main outcome and treated repeated measurements from the same people as independent data points⁷. They also noted that four volunteers who declined broad data sharing were all in one diet-order group, which could skew the results⁷.

Check who paid, as you would for any study. Hall’s reply was funded by the NIH’s in-house research program, and its authors reported no financial conflicts⁷. The record of the Ludwig team’s paper that we reviewed didn’t list its funding⁶.

Where that leaves you

No long, tightly controlled trial has settled the question, and short ward studies haven’t shown that lowering insulin, by itself, melts more fat. Supporters of the model say the right tests would run longer⁶.

For weight, then, the insulin theory remains unproven. Whether cutting carbs helps blood sugar in diabetes is a separate question, covered in our low-carb article.

A fasting insulin number depends on the lab

Clinics and online labs will measure your fasting insulin for a fee. The number looks precise. It may not be.

In a 2025 study in the journal Clinical Chemistry and Laboratory Medicine, researchers ran 40 blood samples through 12 commercial insulin tests from nine manufacturers⁸. They compared each with mass spectrometry, a highly accurate reference method⁸.

Only one test fully agreed with the reference⁸. Several read high at low insulin levels and low at high levels, even though all claim to be calibrated to the same World Health Organization standard⁸. The NIH-funded authors called for urgent standardization⁸.

That matters because a “fasting insulin” or HOMA-IR result is only as good as the test behind it. Our companion article on insulin resistance explains why doctors rarely order these numbers and which standard tests they use instead.

Needing insulin is biology, not a verdict on willpower

In type 1 diabetes, the pancreas loses its insulin-making beta cells³. Without a daily supply, most people with type 1 could not survive, NIDDK says¹⁰. In 2021, about 1.7 million U.S. adults ages 20 and up had type 1 diabetes and took insulin¹⁰.

Type 2 diabetes works differently. The body’s response to insulin weakens, and the pancreas can’t make enough extra insulin to make up for it³. Doctors may add insulin to pills or other injected medicines, and some people need it only for a while, such as during pregnancy or a hospital stay⁹. NIDDK calls insulin safe during pregnancy⁹.

Many people still dread it. Reluctance to start insulin, sometimes called psychological insulin resistance, shows up in about 40% to 70% of patients, depending on how it’s measured, according to a 2016 editorial in the Hong Kong Medical Journal¹¹. A U.K. survey cited there found about a five-year lag before insulin was started¹¹.

Some people treat the first injection as a penalty for not managing their diabetes well, the editorial noted¹¹. That reluctance is tied to higher A1C levels and to depression¹¹. Waiting has a cost.

A word on natural values

Many natural-health readers prize the body’s own wisdom. Insulin fits that value better than it may seem. It is a hormone your own pancreas makes, and for someone whose beta cells can no longer keep up, insulin treatment supplies what’s missing.

The Toronto team’s one-dollar patent also reflected an ethic many readers share: no one should hold a private monopoly on a lifesaving medicine². Wanting fair prices and wanting the medicine are not in conflict.

Insulin claims, checked

This scorecard is our own, built from the sources in this article. Ratings use our four-level evidence scale.

Claim	What the evidence shows	Rating
Cutting carbs lowers the insulin your body releases	Insulin output was lower on the low-carb diets in two NIH ward studies57	Strong evidence (short term)
With calories equal, lowering insulin speeds fat loss	In the 2015 ward study, the low-fat diet lost more fat in six days5; model supporters say longer trials are needed6	Evidence says no (short term)
Diet-driven insulin is the main cause of weight gain	No long, tightly controlled trial has tested it, and leading teams disagree over the short ones67	Not enough evidence
Insulin medicine can cause weight gain	NIDDK lists weight gain among side effects to discuss9	Strong evidence
Insulin is only for type 1 diabetes	Some people with type 2 or gestational diabetes need it too9	Evidence says no
A fasting insulin test tells you exactly where you stand	Only 1 of 12 commercial tests matched a reference method8	Evidence says no
Needing insulin for type 2 means you failed	Type 2 involves the pancreas falling behind; some people need insulin only temporarily39	Evidence says no

Insulin got cheaper for many people, but not for everyone

The one-dollar patent didn’t keep prices low forever. A July 2026 report by the federal Office of the Assistant Secretary for Planning and Evaluation (ASPE) cites research on four leading insulins¹². Their gross sales roughly doubled between 2012 and 2019, to $27.0 billion from $13.0 billion¹².

Net sales, the money makers kept after rebates and discounts, shrank in those years to $5.0 billion from $8.1 billion¹². List prices and real prices had drifted far apart. In 2018, 19% to 31% of insulin users in different private insurance markets paid more than $35 a month for a product, ASPE noted¹².

Then prices broke. In March 2023, Eli Lilly announced 70% list-price cuts for Humalog and Humulin, Novo Nordisk announced cuts of up to 75% for NovoLog, and Sanofi announced a 78% cut for Lantus¹². Most took effect in late 2023 or January 2024¹².

Medicare moved, too. Under the Inflation Reduction Act, Part D enrollees have paid no more than $35 a month for each covered insulin, with no deductible, since January 2023¹². The same cap reached insulin used in pumps under Part B in July 2023¹².

On January 1, 2026, Medicare’s first negotiated drug prices took effect in Part D¹³. For NovoLog and Fiasp, the price is $119 for a 30-day supply, compared with a $495 list price¹³. Trade press put that at 76% below the 2023 list price, which was set before Novo Nordisk’s own list-price cut took hold¹²¹⁵.

From 2026 on, the monthly cap is the lowest of $35, 25% of Medicare’s negotiated price, or 25% of the plan’s own price¹². By our math, 25% of $119 is $29.75, so a month of these insulins should cost enrollees about $30 at most; check your plan’s statement.

The average out-of-pocket cost of a month’s supply fell sharply between 2018 and 2025, in 2025 dollars¹²:

• Medicare: from $42.79 to $12.04
• Private insurance: from $39.13 to $18.26
• Cash or assistance: from $212.81 to $70.93

Gaps remain. The American Diabetes Association counts 29 states plus the District of Columbia with insulin copay caps, ASPE reports¹². Those state laws generally don’t reach self-funded employer plans, and such plans covered 63% of workers with job-based insurance in 2024¹².

Copies are arriving. In 2021, Semglee, a version of the long-acting insulin glargine, became the first biosimilar of any drug to earn FDA’s interchangeable status¹². An interchangeable version of insulin aspart, Kirsty, followed in July 2025¹².

Lows are the main danger when habits change

Eating fewer carbs, fasting and exercising more are common natural-health changes. For someone taking insulin or certain pills, each can push blood sugar too low¹⁴.

NIDDK lists the people at higher risk: those with type 1 diabetes, people taking insulin, sulfonylureas or meglitinides, adults 65 and older, and people with kidney disease, heart disease or past lows¹⁴.

Common triggers include eating fewer carbs than usual, skipping or delaying meals, fasting while on glucose-lowering medicine, and drinking alcohol without food¹⁴. Extra physical activity can lower blood sugar for up to 24 hours¹⁴.

So make diet and activity changes a team project. Ask your care team which of your medicines can cause lows and how your plan should change¹⁴. Never change an insulin dose on your own.

Know the signs. Shakiness, hunger, tiredness, dizziness, confusion and irritability can all signal a low¹⁴. At night, watch for nightmares, crying out or sweat-damp sheets¹⁴.

Treat it fast. For a reading under 70 mg/dL, or below your own target, NIDDK advises 15 to 20 grams of fast carbohydrate, such as four glucose tablets or half a cup of juice, then a recheck after 15 minutes¹⁴. Repeat if still low¹⁴.

Know the emergency. A severe low can cause seizures or loss of consciousness¹⁴. Glucagon by injection or nasal spray is the best treatment, and others should call 911 right after giving it, or right away if no glucagon kit is on hand¹⁴.

Especially in type 1 diabetes, high ketones are the other emergency. Extreme tiredness, trouble breathing, fruity-smelling breath, fainting, belly pain, nausea or vomiting can signal diabetic ketoacidosis, which needs treatment right away¹⁰.

Questions readers ask

The bottom line

Insulin is the hormone that clears sugar from your blood after meals, and for millions of people it is the difference between life and death. Its discoverers treated it as a gift to the world. After decades of high list prices, many Americans now pay far less, though cash payers and some insured people still face gaps.

The claim that insulin makes you fat is a serious hypothesis, not a settled fact; controlled tests so far haven’t shown that lowering insulin alone speeds fat loss. If you use insulin, needing it says nothing about your character. Plan any diet or activity change with your prescriber, know the signs of a low, and never ration doses.

Related reading

• Insulin resistance is common even without obesity, and its popular test isn’t standard
• Low-carb can mean 20 grams or 200, and what replaces the carbs matters most
• Keto is real medicine for epilepsy, but its edge for weight loss is small
• Some healthy habits clash with your medicines, so check these goals first
• Cut your medical bills without cutting the care

Sources

1. Harris J. “The First Insulin Injection as a Treatment for Diabetes.” Origins: Current Events in Historical Perspective, Ohio State University, January 2022. origins.osu.edu
2. University of Toronto, Thomas Fisher Rare Book Library. “The Manufacture of Insulin.” The Discovery of Insulin at the University of Toronto (online exhibition). fisherdigitus.library.utoronto.ca
3. National Institute of Diabetes and Digestive and Kidney Diseases. “Story of discovery: how different medications for diabetes and obesity emerged from basic research on one pancreatic hormone.” NIH, January 27, 2021. niddk.nih.gov
4. Luzi L, DeFronzo RA. “Effect of loss of first-phase insulin secretion on hepatic glucose production and tissue glucose disposal in humans.” American Journal of Physiology, 1989 (UT Health San Antonio record). scholars.uthscsa.edu
5. Hall KD, Bemis T, Brychta R, et al. “Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss than Carbohydrate Restriction in People with Obesity.” Cell Metabolism, 2015 (University of Michigan journal-club summary). bridgeslab.sph.umich.edu
6. Soto-Mota A, Jansen LT, Norwitz NG, Pereira MA, Ebbeling CB, Ludwig DS. “Physiologic Adaptation to Macronutrient Change Distorts Findings from Short Dietary Trials: Reanalysis of a Metabolic Ward Study.” Journal of Nutrition, 2024 (University of Minnesota record). experts.umn.edu
7. Sciarrillo C, Guo J, Hengist A, Darcey V, Hall KD. “Flawed Reanalysis Fails to Support the Carbohydrate-Insulin Model of Obesity.” Preprints.org, January 2024 (published in Journal of Nutrition, 2024). preprints.org
8. Rohlfing C, Petroski G, Hatten-Beck M, et al. “The current status of serum insulin measurements and the need for standardization.” Clinical Chemistry and Laboratory Medicine, 2025. pubmed.ncbi.nlm.nih.gov
9. National Institute of Diabetes and Digestive and Kidney Diseases. “Insulin, Medicines, & Other Diabetes Treatments.” NIH, reviewed March 2022. niddk.nih.gov
10. National Institute of Diabetes and Digestive and Kidney Diseases. “Type 1 Diabetes.” NIH, reviewed February 2025. niddk.nih.gov
11. Luk A. “Psychological insulin resistance: scope of the problem.” Hong Kong Medical Journal, 2016. hkmj.org
12. Murphy S, Smith SR, Sun E, Mulligan C. “The Changing Insulin Affordability Landscape: Lower Out-of-Pocket Costs and Expanded Access Pathways.” HHS Office of the Assistant Secretary for Planning and Evaluation, July 20, 2026. aspe.hhs.gov
13. U.S. Pharmacist. “Negotiated Medicare Price Discounts to Begin in 2026.” August 20, 2024. uspharmacist.com
14. National Institute of Diabetes and Digestive and Kidney Diseases. “Low Blood Glucose (Hypoglycemia).” NIH, reviewed July 2021. niddk.nih.gov
15. Healio. “Medicare announces price cuts for 10 drugs in first round of drug price negotiations.” August 15, 2024. healio.com