The Surprising Benefits of Taking Metformin for Type 1 Diabetes

Editor’s note: This article includes Ginger’s personal experience taking metformin in addition to her daily insulin regimen as a person with type 1 diabetes. Remember, Ginger is not a doctor—and she is definitely not your doctor. What has worked for her may not work for everyone. Please consult your health care team before making any changes to your diabetes management regimen. 

I’ve lived with type 1 diabetes for almost 25 years. About five months ago, I started taking metformin. At first, the impact on my insulin sensitivity was minimal. But the longer I’ve been taking it, the more I experience the benefits.

(Spoiler alert: It’s preventing that morning spike from dawn phenomenon and I’ve even lost 6 pounds of stubborn weight!)

Here’s a look at why I started taking it and how it’s affecting my diabetes management.

Five ways metformin could help a person with type 1 diabetes

Yes, metformin is initially intended for type 2 diabetes—not type 1. But it is not off limits for people with type 1 diabetes (T1D)—it can be helpful in several ways when taken along with your basal and bolus insulin. The benefits of metformin in T1D have been studied! (Read here and here.) There are many benefits of metformin unrelated to diabetes, too.

(To be extra clear: metformin cannot replace your need for insulin if you have T1D.)

Here are 5 ways metformin could benefit a person with T1D:

1. Metformin can help compensate for the fact that you don’t produce the hormone amylin. Amylin is a critical hormone that the pancreas produces—unless you have T1D. In T1D, the immune system attacks the islet cells produced by the pancreas. Those islet cells then secrete beta cells—which produce insulin—and alpha cells, which produce amylin! Amylin works in several ways: reduces the amount of glucose your liver produces, tells your brain you’re full during/after eating and prevents post-meal spikes in your blood sugar by slowing down how quickly you digest food.
2. Metformin reduces the amount of glucose (sugar) your liver produces. Your liver releases stored glucose (known as glycogen) drip-by-drip all day long. By reducing your liver’s glucose production, you’ll also reduce the amount of basal insulin your body needs. The less glucose we produce and the less basal insulin we need, the less likely we’re storing excess glucose as body fat. Remember, this can also apply to morning liver glucose triggered by dawn phenomenon hormones! Your body’s lack of amylin production inevitably means your liver is producing more glucose than normal.
3. Metformin reduces your appetite and reduces post-meal spikes in your blood sugar. It does this by slowing down how quickly your stomach empties digested food into your small intestines where the glucose then enters your bloodstream. By slowing down this process, metformin can curb the post-meal spike you’ve battled with pre-bolus insulin and stress! This also inevitably decreases your appetite by helping you feel full sooner and longer after eating. 
4. Metformin reduces how much glucose (sugar) you absorb from the food you eat. By blocking how much glucose you absorb from digested food, it reduces how much glucose affects your blood sugar. This will have a clear impact on how much insulin you need for the food you eat. 
5. Metformin increases your body’s sensitivity to insulin. Whether that insulin was produced by your own pancreas or taken via injection/pump, metformin increases your cells’ ability to use that insulin. This inevitably means you’d need less insulin overall.
6. Metformin can lead to B-vitamin deficiency. This isn’t a deal-breaker. It just means you should take a B-vitamin supplement and your doctor should check your B-vitamin levels now and then.

Seven tips for taking metformin with type 1 diabetes

Between potential side effects and the positive impact metformin can have on your diabetes, here are a few things to keep in mind while taking metformin if you have type 1 diabetes. (Many of these also apply to taking metformin with type 2 diabetes).

1. Metformin can cause digestive side effects in some people. Metformin’s potential digestive side effects include primarily diarrhea, nausea, frequent bowel movements, bloating, and gas. Personally, I experienced two very mild days of visiting the latrine more frequently. For many people, these side effects will dissipate after the first few weeks on the drug. For others, they can be persistent. And many people experience no digestive side effects at all. Side effects can be lessened significantly by starting with the lowest dose (500 mg) of the “extended release” version. Your doctor might gradually increase the dose after a month. Also, always take metformin with food—never on an empty stomach.
2. Metformin is more effective the longer you take it. Patience and consistency are critical! As you’ll read in my personal experience below, metformin can take a little while to really get going—so stick with it for at least six months before concluding how effective it is for you.  
3. The timing of your metformin matters—even with the “extended release” version. While it’s prescribed to be taken with meals, I personally switched from taking it with meals to taking my 1000 mg dose right before bed. This timing worked well for me because I wanted the biggest impact to hit when dawn phenomenon hormones would normally spike my blood sugar 100 points at 6 a.m. Over time, metformin definitely reduced all of my insulin needs (meals, corrections and basal insulin), but in the first couple of months, I saw the biggest impact about five hours after taking it. 
4. Metformin can lead to low blood sugars and require immediate and long-term changes in your insulin doses. Yes, if you start taking a medication that decreases your body’s need for insulin, you’ll have to keep a careful eye out for lows. Those recurring low blood sugars mean it’s time to adjust your insulin doses with support from your health care team. The longer you’re on metformin, the more likely you’ll continue to reduce your mealtime, correction and basal insulin doses.
5. Metformin changes how quickly you digest food—which changes how you dose insulin. In my experience, metformin can delay the impact of my meal on my blood sugar by at least 30 minutes, and sometimes more. This means I need to adjust how I take my insulin, too, because I don’t want the insulin to hit before the food dose. When taking large doses for those high-fat/high-carb meals (like pizza, cupcakes, etc.), this is especially important to keep in mind.
6. Metformin’s weight loss effect is slow and steady. This is definitely not a weight-loss drug, but it does tend to help people lose a small amount of weight. The combination of decreased liver glucose decreased insulin and decreased sugar absorbed from food all lend themselves to gradual weight loss. It was only after three months that I personally noticed I was losing one pound of real body fat every month. Nearing the end of five months as I type this, I’m almost down 6 pounds of stubborn chub that no amount of jumping rope, jogging and clean eating would budge.
7. Metformin is one of the cheapest drugs on the planet. Metformin costs me about $3.61 per month out-of-pocket. I would’ve loved to try something more powerful than metformin—like Ozempic (semaglutide)—but my insurance company said I didn’t qualify. So, I asked my doctor for a prescription for metformin to address my rising insulin needs with the hope that it might impact my dramatic dawn phenomenon, too. While he wasn’t experienced in prescribing it for type 1 diabetes, he agreed that it could be helpful. My insurance didn’t believe I had enough insulin resistance to qualify for Ozempic, they easily approved my request for metformin to address the exact same issue.

Before metformin vs. five months later

I’ll give you the month-by-month breakdown in a moment. But first, here’s the “before” and “after” stats:

My diabetes stats before starting metformin:

• Weight: 127 pounds (at a height of 5’2)—I had slowly crept up to this over the course of the last year.
• A1c & goal range: 5.7 to 6.3 percent
• Long-acting insulin dose: 15 units (rising from 9-11 units just a year before)
• Insulin-to-carbohydrate ratio: 1:10 to 1:15 (1 unit of insulin for every 10-15 grams of carb)
• Dawn phenomenon spike: Hits at 6 a.m. and spikes 100 to 150 points. I need 1 unit of rapid-acting injected insulin carefully timed around my morning exercise to prevent that dramatic spike.

My diabetes stats after five months of metformin:

• Weight: 121 pounds (at a heigh of 5’2)—a slow and steady loss that wasn’t visible until after three months.
• A1c: still in my goal range of 5.7 to 6.3
• Long-acting insulin dose: 10 units—a significant reduction, back to my usual baseline.
• Insulin-to-carbohydrate ratio: 1:30 (1 unit of insulin for every 30 grams of carbohydrate—I need significantly less insulin for my meals.
• Dawn phenomenon spike: I rise only about 30 points when I first wake up. I don’t see a more dramatic rise until 9 a.m. if I choose to practice intermittent fasting and skip breakfast (if ya don’t eat breakfast, your liver releases stored glucose to give you energy). I can prevent that spike with a ½ unit of rapid-acting injected insulin. I no longer worry about dropping low during morning fasted exercise!

Months one-to-five: My gradual results with metformin

The longer I take metformin, the more I see the benefits. Taking it consistently and being patient are critical.

• After just two days on metformin (500 mg dose) taken midday: I reduced my long-acting insulin from 15 units to 14 units because I was running very low between meals.
• After two weeks on metformin (500 mg dose) taken midday: I reduced my long-acting insulin to 13 units. I need significantly less insulin for meals eaten within four to eight hours after taking metformin dosage. Still experiencing dawn phenomenon spike.
• After two months on metformin (1000 mg dose) taken at bedtime: I reduced my long-acting insulin to 12 units. I need about 25 to 50 percent less insulin with my meals. My dawn phenomenon spike is significantly lower, rising by only 30 points between 6 to 9 a.m. Then I might need to take ½ of rapid-acting insulin to manage liver glucose due to intermittent fasting. *The big difference here is that I started taking metformin before bed so the breakdown of the medication is timed well with dawn phenomenon.
• After three months on metformin (1000 mg dose) taken at bedtime: I reduced my long-acting insulin to 10 units. I need significantly less insulin with carbohydrates eaten before bed and at daytime meals. My dawn phenomenon spike continues to usually be no more than 30 points between 6 to 9 a.m. Then I might need to take ½ of rapid-acting insulin to manage liver glucose due to intermittent fasting. This is also when I noticed my weight was decreasing despite no other significant changes in my lifestyle. 
• Today, after five months of taking metformin (1000 mg dose) taken at bedtime: By month five, I can simply tell you: I feel more satisfied after eating. I need dramatically less insulin for carbohydrates (even grapes or Hershey’s chocolate). I have a much easier time managing and preventing spikes from dawn phenomenon. My weight continues to decrease ever-so-gradually. My basal insulin dose is down to 10 units and I wouldn’t be surprised if I need to decrease it to 9 units eventually if I continue to drop another pound.

Consistency + patience is critical when taking metformin

At first, I wasn’t impressed with the impact on my insulin needs. But I’m glad I kept taking it anyway—after five months, it was obvious that metformin is hugely affecting my insulin needs, my weight, my appetite and my body’s production of glucose at 6 a.m.

The benefits of metformin absolutely make sense in supporting a person with type 1 diabetes—and it’s a very affordable medication. Talk to your health care team if you think taking metformin might help you with your diabetes management goals! 

WRITTEN BY Ginger Vieira, POSTED 09/29/22, UPDATED 05/18/23

Ginger Vieira is an author and writer living with type 1 diabetes, celiac disease, fibromyalgia and hypothyroidism. She’s authored a variety of books, including “When I Go Low” (for kids), “Pregnancy with Type 1 Diabetes,” and “Dealing with Diabetes Burnout.” Before joining Beyond Type 1, Ginger spent the last 15 years writing for Diabetes Mine, Healthline, T1D Exchange, Diabetes Strong and more! In her free time, she is jumping rope, scootering with her daughters, or walking with her handsome fella and their dog.