Somewhere in a hospital right now, a physician is ordering a sliding scale of short-acting insulin to be given before a meal, at a dose set by the premeal blood glucose. Not a correction dose for hyperglycemia on top of a meal dose. The meal dose. Blood glucose before a meal describes what has already happened. It says nothing about whether the tray holds 20 g of carbohydrate or 90. Premeal insulin dose and premeal blood glucose have nothing to do with each other, hyperglycemia correction notwithstanding. Basing a dose of premeal insulin only on the premeal blood glucose is to not understand basic physiology, and it needs to stop.
It is wrong on the wards and it is wrong in clinic. These sliding scales go home with patients at discharge, and I see them written by endocrinologists, people who did a fellowship in this. Inject 4 units for a glucose of 150 to 200, 6 units for 201 to 250, etc., etc., and nowhere does anyone ask what the patient is about to eat.
Elliott Joslin published his scale in 1934, in the 5th edition of A Diabetic Manual for the Mutual Use of Doctor and Patient. It ran on urine. You boiled the sample with copper sulfate and read the color: Blue meant no insulin, green 5 units, yellow 10, orange 15. Rainbow coverage, people called it. Joslin was not a fool. He had regular insulin and a copper sulfate assay and that was the toolkit.
What he fed those patients is the part nobody mentions. The Joslin diabetic diet of 1923 was about 5 percent of calories from carbohydrate, 20 percent protein, 75 percent fat. That is 1923, a year into the insulin era. Joslin regarded dietary carbohydrate as serving no useful purpose in a diabetic. Then the profession decided insulin made all of that unnecessary, carbohydrate came back through the 1920s and 1930s, and the scale outlived the diet it was built for.
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The meals kept going the wrong way. In 1979, the American Diabetes Association (ADA) put carbohydrate at 50 to 60 percent of calories. In 1992, the U.S. Department of Agriculture stacked 6 to 11 daily servings of bread, cereal, rice, and pasta at the base of the pyramid and called it balance, and diabetics were handed the same picture. The ADA has since backed off to individualization and allows that low-carbohydrate patterns are viable, 30 years late. It has never endorsed a very low-carbohydrate diet. Neither have the clinics with Joslin’s name on the door, whose nutrition guideline for overweight adults with type 2 diabetes puts carbohydrate at 40 to 45 percent of calories with a floor of 130 g a day. Forty-five percent of 2,000 calories is 225 g of carbohydrate a day. And the guideline concedes that on a 1,000-calorie plan that floor is about half of total calories, so the floor overrides the percentage in exactly the patients told to lose weight. That is the meal the sliding scale is being asked to cover.
The scale fails in the two obvious directions. Glucose at target and a large meal, it underdoses. Glucose high and a small meal, it overdoses, and somebody is treating a low three hours later. Now and then the two numbers line up by accident, the patient does fine, and that gets filed as evidence the thing works. Insulin sliding scale does not work because it does not address fundamental physiology, which is the necessity of matching carbohydrates with the appropriate amount of insulin. What it does accomplish is an illusion of doing something that appears sophisticated on the surface. There are, after all, low-dose, regular-dose, and high-dose sliding scales. The task of changing hospital and outpatient diets and patients’ habits entrenched by decades of misguided advice is near-impossible; sliding scales, on the other hand, are available at the click of a button and give prescribers a false idea of accomplishing an important task.
None of this is new. A 1970 paper in the Journal of the Kentucky Medical Association called sliding scale adjustment a fallacy. A 1997 cohort study in Archives of Internal Medicine found no benefit. A 2007 paper in the American Journal of Medicine asked whether it was myth or insanity. A 2009 JAMA commentary told us to stop sliding. It went nowhere. Sliding scales are still ubiquitous.
Better carbohydrate counting is not the answer either. Practically speaking, most patients do not do it, and those who do cannot do it accurately enough. The error scales up with the carbohydrate load. At 1 unit per 10 g, a 20 percent miss on a 75 g plate is 1.5 units; on a 15 g plate it is 0.3. No or low carbohydrate at meals makes the error small or negligible. Stop trying to improve the guess. Make the thing being guessed at smaller.
In type 2 this often ends prandial insulin outright. The 12 units at dinner existed because dinner was 90 g and whatever beta-cell function remained could not cover it. Remove the 90 g and there is nothing left to dose against. I have taken people with type 2 diabetes off bolus insulin entirely and decreased their basal insulin, in every patient who actually listened to me and dramatically reduced their carbohydrate intake. Type 1 is different. The disease does not go anywhere and prandial insulin stays mandatory. But a few units of ultra-rapid insulin against a small, mostly protein and fat meal is a task a human being can perform. Fat and protein are not metabolically silent. They produce a later, smaller, flatter rise, and a fixed few units handle that far better than any dose handles 90 g.
Two cautions. Cut the insulin or sulfonylurea dose the same day you cut the carbohydrate, and think about euglycemic ketoacidosis before running restriction alongside a sodium-glucose cotransporter-2 (SGLT2) inhibitor.
Biologically, a low-carbohydrate diet works every time, and the failures are failures of adherence, not of mechanism. I have watched it work for close to 25 years. And no trial has ever shown that dosing mealtime insulin off a premeal glucose controls postprandial glucose. The trials we have show the opposite.
So here we are in 2026, after 56 years of blistering critique, running a 92-year-old algorithm designed around a copper sulfate urine test, on patients wearing continuous glucose monitors, eating the opposite of what its author prescribed.
This essay is cited in the KevinMD record on diabetes and obesity.
Michael Duben is a board-certified endocrinologist in solo private practice in Fairfield, Connecticut, and is affiliated with Bridgeport Hospital. He runs both Endocrinology of Fairfield County, a traditional insurance-based practice, and Restore Health, a cash-based functional endocrinology practice. He completed the Institute for Functional Medicine’s training program.
He did his internal medicine residency at Mount Sinai and his endocrinology fellowship at Montefiore/Einstein, and was a clinical instructor in the Department of Endocrinology at Albert Einstein College of Medicine. He has practiced since 2003, with clinical interests in thyroid disease and thyroid cancer, osteoporosis and bone metabolism, parathyroid disease, pituitary disorders, and obesity and metabolic disease. He has prescribed glucagon-like peptide-1 (GLP-1) receptor agonists since the first one reached the market in 2005, and has lectured to practicing physicians on diabetes and thyroid management.
He designed and built the HIPAA-compliant AI-assisted clinical documentation system he uses in daily practice, without formal training in computer science, along with a range of other tools for his patients and his office. He shares updates on LinkedIn.
