Naturally, people whose lives depend on taking insulin get very nervous at the thought of not having access to it. We can’t help but wonder: in the worst-case scenario, just how long would we be able to hang on without it?

Conventional wisdom says the answer is roughly 3-4 days. But is that really true?

We set out to do some fact-checking.

First, let’s talk about the physical process that sets in when a person with diabetes does not get enough insulin into their body.

Very quickly, severe hyperglycemia sets in. That is high blood sugar that leads to a state called DKA, short for diabetic ketoacidosis, which — untreated — leads to death.

Basically what’s doing on is this: insulin helps sugar enter the cells, which use it for fuel. Without insulin, the body cannot access enough sugar to function properly, so your liver begins to turns some of the body fat into acids called ketones. These build up in the bloodstream and spill over into the urine. When these excess ketones get into the blood, the blood becomes acidic, causing DKA: a combination of very high blood sugar, dehydration and shock, and exhaustion.

Symptoms are vomiting and hyperventilation, and eventually passing out and going into a coma. Without treatment, this leads to death.

Generally, the first signs of DKA show up once the blood glucose level has been north of 300 mg/dL for about four hours, but how quickly things get out of hand at that point is highly variable. Some people with diabetes feel ill immediately, while others can wander around in a daze for days.

If you have any residual insulin at all in your system, it can help hold off DKA even when your blood sugar level is high, according to Dr. Silvio Inzucchi, clinical director of the Yale Diabetes Center.

Hospitalizations for DKA are unfortunately on the rise in the United States.

There is no single definitive answer to that question, says Dr. Francine Kaufman, renowned endocrinologist, author, professor and current chief medical officer of implanted glucose sensor company Senseonics.

She breaks it down this way:

  1. People with type 2 diabetes who take insulin “could last quite a bit of time — maybe years — depending on how their other meds might be working.
  2. New-onset type 1s “might have some remission phase and residual insulin secretion.” Similar to what doctors saw before the discovery of insulin, “people could last months to maybe a year, particularly on a carbohydrate-restricted diet.”
  3. A LADA (latent autoimmune diabetes in adults) patient might have some residual insulin as well and might last days or weeks, or maybe even longer, again depending on how much insulin is left. “One might be able to assess by how much insulin they take on a routine basis. If it is about 20 units a day or less, that might indicate they have residual insulin” being produced in the pancreas.
  4. For people with “regular” type 1 diabetes, particularly those diagnosed in childhood or adolescence, to survive without insulin, “they would need to stay on carbohydrate restriction and stay very hydrated,” Kaufman says. But their survival rate is “multiple days, to a few weeks, getting sicker and weaker as time goes on. Even a little insulin a day would help prolong this, particularly long-acting insulin. Exercising would not be beneficial to bring glucose down… too much physiologic stress that could elevate glucose further.”

The risk for people with type 1 is a quick death from DKA (insulin deficiency exacerbated by illness stress dehydration). “It only takes days to progress, and it is worsening over a day or two or three — so that gets you a week or so plus/minus, outside maybe two weeks,” Kaufman explains.

In fact, DKA from lack of insulin is the leading cause of death of children with type 1 in Africa. But it’s difficult to get any hard data on how many hours/days/weeks/or months these T1Ds last without insulin.

Yale’s Dr. Inzucchi also says this is a tougher question than it appears on the surface. He points out that many type 1s can have some “residual beta-cell capacity” even sometimes years after diagnosis. He tells us that how fast DKA advances also depends on how well you keep yourself hydrated, and how many carbs you are consuming that will “feed the highs.”

“I will see that in someone with 0% insulin production, they’ll begin to fall ill within 12-24 hours after their last insulin injection, depending on its duration of effect. Within 24-48 hours they’ll be in DKA. Beyond that, mortal outcomes would likely occur within days to perhaps a week or two. But I could not see someone surviving much longer than that.”

First of all, be aware of the symptoms, if any. Our own DiabetesMine correspondent Wil Dubois, who landed in the hospital with DKA last year, writes:

“The main symptoms of DKA that we’re told to watch for — other than those associated with high blood sugar in the first place, like crazy thirst and peeing like a race horse — are nausea or vomiting, abdominal pain, fruity-smelling breath, rapid breathing, and confusion.”

“Of course, you can’t smell your own breath. If you are confused you probably don’t know it. And most people aren’t aware of their respiration rate. So the main warning sign of impending DKA that all type 1s are taught to be alert for is the union of nausea and abdominal pain in the presence of high blood sugar. And I never had any. Nausea or pain, but clearly as my doctor noted, I was experiencing DKA.”

If you know that you have missed a shot or are running low / rationing insulin, it’s a good idea to keep very close tabs on your blood sugar readings and keep ketone test strips handy.

“For someone with established type 1 diabetes, if they really face a limitation of their insulin supply, don’t let it run out completely! Stretch it out,” encourages Inzucchi.

Basal insulin, the long-acting “background” type, continues to have some effect for a full day or more after the last shot. So it would be a good idea to ration that type above all. This also underscores why it’s important for people who use insulin pumps — which only contain rapid-acting insulin — to also have basal insulin stored for emergencies.

We hate to break it to you, but they didn’t.

Looking at historical records from pioneering diabetes doctors Joslin and Allen before the advent of medical insulin, we see that they were only able to keep patients alive for months, sometimes more than a year, by starving them to death. Literally.

Dr. Elliott Joslin proudly wrote that, “Whereas formerly the prognosis for children less than 10 years of age was measured in months, today it is rare for a child to live for less than one year.” Ultimately, all of Joslin’s pre-insulin patients died. 100 percent of them. Those who didn’t starve succumbed once their insulin production dropped to zero.

But of course we now know that the onset of type 1 is a messy affair. The autoimmune process that drives it doesn’t happen overnight. Insulin production lingers for many months in a phenomenon called the diabetes honeymoon.

So, history can only show us how long we can suffer starved in the honeymoon phase of the disease, not how long a full-fledged type 1 will last sans insulin in today’s modern world.

DKA is the leading cause of death in people with T1D under age 24. But stats indicate that there are only several-thousand deaths from DKA per year in the whole country. Most cases occur right at disease onset, and most receive some sort of medical intervention in a timely manner. The CDC reports that in-hospital fatality rates from DKA declined during 2000–2014 at an annual average rate of 6.8 percent.

So the odds for survival are much more in our favor than they ever have been, historically speaking.