# Effects of metformin on running performance



## AndyC

Hi

I've been a recreational jogger for many years and a club runner for the last 4 years. I've got my 5k time down to about 20 minutes. My BMI is 21.

Now unexpectedly at 59 I've just been diagnosed with diabetes - probably type 2 - and prescribed metformin.

Within a few days of starting the metformin I've started to feel incredibly sluggish on easy training runs, with no strength in my legs. It feels as if I had done a marathon the day before.

I've looked up some studies that suggest metformin reduces strength and increases heart rate during exercise.

As I have a 10k race coming up I am starting to worry.

Does anyone have any personal experience of the effect of metformin on their running performance?


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## Northerner

Andy, welcome to the forum  I would say it's highly unlikely to be the metformin at fault, as it takes a couple of weeks at least to 'get into your system' and start to be effective.

How did you come to be diagnosed? My immediate thoughts are that your diagnosis is unusual, given your physique and fitness levels. Is there a history of diabetes in your family? Did you have symptoms for long prior to diagnosis? 

The reasons why I am asking this is that you sound very similar to me. I am also a runner, have been for many years, and my BMI was similar to yours prior diagnosis. However, I am not a Type 2, but Type 1. Frequently, a diagnosis will be made on the basis of age, and your age would suggest Type 2. However, there are a number of people here who have been misdiagnosed because of this and there is then a delay on them receiving appropriate treatment. I was 49 at diagnosis, due to run a marathon that week, but although I had had symptoms for about 18 months, which I had largely ignored, things rapidly went downhill in the space of a few days and I ended up in hospital. 

Do you have a meter so that you can test your blood sugar levels at home? If not, I would advise you to get one. You may be feeling as you do because your pancreas is not producing enough insulin and your blood glucose levels are climbing rapidly - this will severely impair your ability to train and could be potentially dangerous. Given the fact that only your age suggests you are Type 2 I would recommend going back to your doctor, possibly asking to be referred to a consultant for assessment. The sooner you have confirmation of your Type (and there are some tests they can do that will help determine this), the sooner you can be sure you are receiving the right treatment.


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## Mark T

Welcome to the forum AndyC 

I must admit when I read you post title the first thing that popped into my head was using metformin as a performance enhancement due to the emissions that you typically get and their combustibility - but my brains obviously returned to that of an 8 year old today.

I'm with Northerner here, you might but to get referred for a bit of a closer look.  It generally takes at least two weeks (up to a month) for metformin to start having an impact on your body.

However, what metformin does do is impede the liver from dripping glucose into the blood stream.  So yes, I would image that would get in the way of exercise since it's that fast glucose your muscles need when doing significant exercise.


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## trophywench

My other thought about this, is for you to contact those awfully nice and exceedingly expert helpful people at Runsweet - 

http://www.runsweet.com/ 

immediately, if not sooner.


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## BigMalc

Welcome to the support group - it is very useful.

I am T2 and a club runner, though not at your speeds, (23.19 5k PB).

I didnt start running till about 4yrs after diagnosis when all the pills I was taking, inc metformin didnt do enough, so cant compare directly but I have found that with any drug changes it can take the body a week or two to 'rebalance' itself and fatigue is one of the ways mine deals with it, almost as if it is saying 'OK, you can change what you are taking in, but just go easy for a week whilst I adjust and get used to it'

I dont think it should be a long term impairment, but as the others have said if it persists seek help without delay.

Good luck

Malc


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## AndyC

Dear all

Thanks very much for all the advice.

To answer Northerner's questions, I didn't have any symptoms at all apart from a tendency to get drowsy in the afternoon, and I was diagnosed more or less by accident: I had a persistent pain in my ribs and went to the NHS online symptom checker to diagnose it, it told me to dial 999, the ambulancemen came out and said the pain was just a muscle pull and my ECG was fine, but they also did a blood sugar test and it was 18 mmol/l. My doctor then did an HBA1C test and it came back as 85. She diagnosed me provisionally as Type 2 diabetes and put me straight onto metformin but she did say it was very unusual for someone with my body type and lifestyle to get Type 2 so she wasn't absolutely definite. They are doing a pancreas ultrasound.

I have a great grandmother who had diabetes and an aunt who has developed it at about the age of 80.

I am due to see my doctor again in a couple of days so I will press to get a definite Type 1 vs. Type 2 diagnosis asap. I'll also get a blood sugar meter and I've signed up to runsweet's forums.

With regard to my running, I've now been on the metformin for a week and I'm starting to feel stronger again. I used to do a 3 mile morning run at 7:30-7:45 mins/m without much effort, then a few days after I started the metformin I was suddenly struggling to do that run at 9:00 min/m. That's when I put my message up on the forum. This morning, 9 days after starting the metformin, I did it at 8:00 min/m and definitely felt better. So maybe BigMalc is right and it is a case of the body getting used to the new drug environment.

Thanks again to all.


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## Northerner

It sounds like you were getting used to the new regime then Andy. I suspect you will get your diagnosis changed to T1, possible LADA (Latent Autoimmune Diabetes in Adulthood) which is a slow-onset version of T1. Let us know how things go at your appointment  

One thing to bear in mind when you get your meter, it can be dangerous to exercise if your blood sugar levels are in the high teens, as this can indicate that you do not have sufficient insulin circulating to move the glucose from your blood to your cells for energy. In such circumstances, your body may have to use a different energy source, such as body fat (which you don't sound as though you have much of!) or muscle. This process produces a toxic by-product called ketones - again, if there is insufficient insulin then the ketones can build up in the bloodstream, raising its acidity and can be extremely dangerous. Exercise can drive this process out of control. Not trying to frighten the living daylights out of you, but something you should be aware of until you know exactly where you stand.

I found the Diabetic Athlete's Handbook really useful in explaining a lot of the science behind what happens when you exercise.


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## AndyC

Just to update people, after two weeks on metformin but still only at 1000mg a day, and meanwhile following a low-GI diet, my BG was down from 14 to 7.5. I don't know whether it was the metformin or the diet but I was very pleased. This is now 2 weeks ago.

I asked my doctor if maybe I had LADA and she said it was very possible and has referred me to a diabetes clinic who will test.

Meanwhile I am now up to 1500mg a day of metformin. I have noticed that while my training speeds have gone back to what they were before I started the metformin, if I skip a 500mg pill in the meal before I train or race I feel far more energetic than I did before my diagnosis. Last week I did an all time PB in a 10k race. So maybe the body gets used to running despite the hindrance of metformin, and then is able to run much better when that hindrance is suddenly taken away?


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## Northerner

Glad to hear that your levels are decreasing Andy, and that you are getting your energy back  I've never taken metformin, so can't really answer your question. It's supposed to inhibit the absorption of carbs by the intestines, so perhaps that has an effect on the energy available to you when you run? Not sure.

Good that they are looking into the possibility of LADA - let us know how you get on. And well done on the PB!


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