Metformin for Type 1 Diabetes: Pros and Cons

Metformin is the most commonly prescribed glucose-lowering medicine in the world, and it is frequently used as a first-line treatment for type 2 diabetes. 

Although the medicine is currently only officially approved by the U.S. Food and Drug Administration (FDA) for treating type 2 diabetes, you may have heard about people with type 1 diabetes being prescribed metformin off-label. 

If so, you may be wondering whether people with type 1 diabetes can take metformin, whether this arrangement is safe, and how metformin works for people with type 1. 

This article will investigate the use of metformin for type 1 diabetes and answer some common questions you might have about the use of metformin in type 1 diabetes.

Close-up of metformin pill

Key Points: 

  • Metformin, when used for type 1 diabetes, is always administered alongside insulin therapy, as it cannot replace the critical function of insulin in managing blood glucose levels in type 1 diabetes.
  • Metformin can help reduce insulin resistance and aid in weight management for people with type 1 diabetes, but it also carries potential side effects like gastrointestinal discomfort, highlighting the need for medical supervision in its use.
  • Ultimately, while metformin offers potential benefits for those with type 1 diabetes, its use should be carefully considered and guided by a healthcare professional, tailoring treatment to each person’s unique health needs and goals.

Table of Contents

Why would someone with type 1 diabetes want to take metformin?

People with type 1 diabetes may be prescribed metformin off-label (in a way not approved by the FDA) to help reduce insulin resistance (a condition in which the body does not use insulin efficiently), to help better manage blood sugar levels, and in some cases for weight loss (usually as a result of addressing insulin resistance). 

Several clinical trials and meta-analyses have shown that taking metformin can lead to modest weight loss. Although this isn’t the most common reason people are prescribed metformin, the drug is known to reduce appetite and help the body be slightly more metabolically efficient, which can lead to weight loss over time.

Learn more in: Metformin and Weight Loss: Can a Pill Help You Lose Weight?

Even though trials have shown that HbA1c levels (a measure of glucose control over the previous 2 to 3 months) do not change significantly for people with type 1 diabetes who start taking metformin, research has found that adding metformin to an existing insulin regimen can help reduce the amount of insulin people need to take each day.

For people with type 1 diabetes, metformin is always used in conjunction with insulin therapy. 

“Back in 2017, I noticed my blood glucose control and A1c plateauing, mostly due to insulin resistance. My doctor recommended that I start taking metformin to help improve my diabetes management.”

Kat Schroeder, T1D (read about Kat’s experience with metformin)

Can metformin replace insulin?

It is not safe for people with insulin-dependent diabetes to attempt to replace insulin with metformin. 

Management of type 1 diabetes requires insulin therapy. This is because if you have type 1 diabetes, your pancreas produces either very little or no insulin. 

This hormone is critical for survival, so it must be externally administered (via injection or infusion) to maintain normal blood sugar levels and ensure the body’s cells receive the glucose they need for energy. 

Without insulin therapy, people with type 1 diabetes cannot regulate their blood glucose levels, leading to serious health complications. Therefore, insulin therapy is not just a treatment but a life-sustaining necessity for people with type 1 diabetes.

Metformin can significantly help lower blood sugar levels, but it doesn’t increase or restore the body’s ability to produce insulin. 

It’s important to consult with your doctor about medications you’re taking to make sure your prescriptions and plan of care are up to date and to help prevent unintended interactions. 

But either way, while metformin can help you better manage your blood sugar levels, the medicine can never serve as a replacement for insulin.

Is taking insulin better than taking metformin?

Neither insulin nor metformin is superior to the other. Rather, they function in different ways to help lower blood sugar levels and can be complementary in certain situations.

In general, metformin is a daily, or twice daily, oral medication that comes in the form of a pill. There are many brands of metformin, along with a variety of combination drugs that include metformin as one of the treatments. 

There are also many kinds of insulin, which are either injected or administered subcutaneously (under the skin) by an insulin pump (or in the case of the ultra-rapid-acting insulin Afrezza, inhaled).

Pros and cons of metformin and insulin

Insulin is an essential hormone that helps sugar from the blood enter the body’s cells to be used as energy. As a general matter, insulin helps to bring down blood sugar levels faster than metformin can. 

Metformin is thought to work by decreasing the release of glucose from the liver and increasing insulin sensitivity in the muscles. 

Despite their benefits, as with all medicines, there are also downsides to both metformin and insulin.

Insulin is a powerful hormone, and taking too much can cause low blood sugar (hypoglycemia), which can be very dangerous, and potentially fatal, if untreated.

Metformin can cause stomach discomfort, diarrhea, and other digestive issues, especially if the dose is too large or if it is taken on an empty stomach. 

See more in: Metformin Dosage Guide (Min and Max Doses).

Clinical trials over many years have established that when metformin alone is not sufficient to manage blood sugar levels for people with type 2 diabetes, combining it with insulin therapy is an effective way to improve control, as measured by HbA1c.

Because people with type 1 diabetes do not produce their own insulin, insulin therapy is necessary for those with this condition, while metformin therapy is not. 

However, because metformin and insulin work differently, researchers are exploring metformin’s potential usefulness in people with type 1 diabetes.

What happens when a person with type 1 diabetes takes metformin?

In 2017, a meta-analysis published in the journal Diabetologia showed that more than 15 percent of adults with type 1 diabetes in Scotland had been prescribed metformin. Additionally, in France, metformin has received approval for treating both type 1 and type 2 diabetes.

The analysis, entitled “A New Perspective on Metformin Therapy in Type 1 Diabetes,” notes that, “perhaps because of such compelling evidence in type 2 diabetes, off-label use of metformin in type 1 diabetes is quite common in clinical practice.”

The research found that people with type 1 diabetes who took metformin in addition to insulin experienced a significant reduction in the amount of insulin they needed to take each day (a nearly 7-unit-per-day reduction) once metformin was added. 

Subsequent research in 2018 reinforced these findings, showing net benefits for people with type 1 diabetes who added metformin to their existing insulin regimen. Introducing metformin was again shown to help with weight management and decreasing daily insulin needs, and it also slightly improved blood pressure.

While there were also some minor improvements in average blood sugar levels, these changes were not significantly different from a group taking a placebo (inactive treatment).

Except for gastrointestinal upset, there were no serious metformin side effects reported from these studies.

As noted by Dr. Leon Gussow in Emergency Medicine News, metformin has been having a moment in the spotlight in recent years due to its possible benefits for improving cardiovascular health, reducing inflammation, and improving all-cause mortality (the risk of death from any cause).

Dr. Gussow is quick to note, though, that the evidence base here is in mice and other laboratory animals — not in humans.

Nonetheless, off-label use for purported general health benefits appears common and can potentially be especially helpful for people living with type 1 diabetes, who are already at a heightened risk for heart disease, stroke, and premature death. 

As with all prescription drugs, metformin should only be taken under the guidance of a doctor or other medical professional, and your medical history and health goals will have a significant bearing on whether or not a metformin prescription is likely to be helpful.

Frequently asked questions

Does taking metformin extend life expectancy for type 1 diabetes?

There is limited evidence showing that taking metformin may extend lifespan, but significant clinical trials are underway to learn more. One of the largest trials working to establish a fact base about metformin’s effects on aging and longevity is known as TAME (Targeting Aging with Metformin).

For now, not enough is known to determine the effects, if any, of metformin on life expectancy, and this is true for both people with type 1 diabetes and without.

At least until more is known, the best bet is to rely on general guidance from your doctor to improve your health and increase your chances of a long life, including taking steps such as keeping your blood sugar levels in range, eating a healthy diet, getting enough exercise, managing stress, and avoiding risky behaviors like smoking cigarettes.

Why is metformin not used for type 1 diabetes more often?

Insulin therapy is absolutely necessary for people living with type 1 diabetes to survive. Metformin, on the other hand, is usually considered to be optional for type 1, and the evidence of its benefits for treating this condition is not currently as strong as for the treatment of type 2 diabetes.

Does metformin lower blood sugar immediately?

No — unlike insulin, which starts to lower blood sugar very quickly, metformin generally takes 2 to 5 days to lower average blood sugar levels.

Some people will not notice effects from metformin for as long as 2 weeks after starting the drug, and some will never see any effect at all.

If you stop taking metformin, the drug will stay in your system for about 4 days, so it’s important to be aware that you may have to adjust your insulin doses when you start or stop taking the medicine.

Read more in: Stopping Metformin: When and How You Can Stop Taking Metformin and How Long Does Metformin Stay In Your System?

Can metformin combination drugs be used for people with type 1 diabetes?

Because the pancreas in type 1 diabetes cannot produce insulin, medications combining metformin with other glucose-lowering drugs are ineffective for this condition.

Learn more in: Metformin Combination Drugs for Type 2 Diabetes.

What happens if I take metformin without being diabetic?

There are plenty of conditions and circumstances that might warrant taking metformin even if you don’t have diabetes. These include conditions like PCOS (polycystic ovary syndrome) or prediabetes (a condition in which glucose levels are elevated, but not high enough to be diabetes).

Read more in: Metformin for PCOS (Benefits and Side Effects) and Metformin for Prediabetes: The Pros & Cons.

Currently, various clinical trials are underway to explore whether taking metformin daily offers health benefits to individuals who are otherwise healthy.

While tests in animals show some improvements in cardiovascular health, inflammation, and decreases in all-cause mortality, these findings are so far tentative and have not been widely demonstrated in people yet.

Is taking metformin safe when you have type 1 diabetes?

Though metformin is generally understood to be quite safe, it’s important to recognize that it does carry some risk of side effects. 

See more in: Metformin Side Effects (Common and Serious)

Metformin can cause upset stomach, vitamin B12 deficiency, low blood sugar, and very rarely — though most seriously — lactic acidosis (a potentially fatal buildup of lactic acid in the bloodstream).

For these reasons, it’s always important to work with your doctor and medical care team to understand the risks and benefits of metformin before taking it.

Learn more in: Is Metformin Safe?

Final thoughts

In summary, metformin, commonly used for type 2 diabetes, is also sometimes prescribed off-label for type 1 diabetes, primarily to manage insulin resistance and assist with weight management. 

It should always be used together with insulin therapy for type 1 diabetes, as it does not replace the need for insulin. 

While it may offer benefits such as reducing insulin dosage and aiding weight loss, it also carries potential side effects such as gastrointestinal discomfort. 

The decision to use metformin for type 1 diabetes should be based on a thorough consultation with your healthcare provider, considering your medical history and health goals.

Suggested next article: Everything You Need to Know About Metformin.


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