How Resistance Training Affects Your Blood Sugar

Healthy Living

How Resistance Training Affects Your Blood Sugar

This post originally appeared on DiabetesStrong.

As I discussed in a recent post, cardio will, for the most part, make your blood sugar drop if you are treating your diabetes with insulin. However, certain types of cardio, like interval training, can actually make your blood sugar increase.

Today I want to discuss how resistance training can affect your blood sugar.

I absolutely love resistance training for three simple reasons:

  1. Resistance training makes me feel strong and empowered
  2. Resistance training has helped me shape my body to my liking
  3. Resistance training ultimately makes my diabetes easier to manage, as it improves my body’s ability to utilize insulin

Resistance training generally falls into two categories

  1. Low-rep (heavy) training with pauses between each set
  2. High-rep training or supersets with little rest between sets. Your heart rate is elevated throughout the workout

Each type of resistance training will affect my blood sugar a little differently during my workouts but they both have the same long-term benefit of a significantly improved insulin sensitivity.

How high-rep workouts affect my blood sugar

In general, I need to be a little more careful and watch my sugars more closely if I do high rep workouts, supersets, or a lot of compound leg exercises (like squats, deadlifts, or lunges). These kinds of workouts will have a cardio-like impact on my blood sugar since my heart rate will be elevated for most of the session.

I treat sessions like these almost as I would treat steady-state cardio – by reducing my pre-workout bolus about 30%-50%.

How low-rep workouts affect my blood sugar

When it comes to more traditional resistance training with fewer reps (less than 10-12 reps per set), the situation is a little different. When doing workouts like this, I sometimes see my blood sugar go up, and sometimes I don’t see much of an impact at all. It basically comes down to what body part I’m training.

For smaller muscle groups like arms and shoulders, my heart rate won’t usually increase that much despite the heavy weight, and my blood sugar will remain stable. If I do heavy chest, back, or leg workouts, however, I’ll most likely see an impact, and it can often be an increase. My body reacts in the same way as when I do an interval cardio workout (see this post to learn why interval workouts make your blood sugar increase).

Given this knowledge, I’ll reduce my pre-workout bolus minimally or not at all for a low-rep workout, depending on the body parts I am training.

How to prepare for resistance training and how to prevent post workout lows

When it comes to resistance training, pre-workout meals play a huge role in whether you’ll be successful in the gym. I always eat something before and after a strength-training workout to make sure I have enough energy to do the workout, to rebuild my muscles, and to maintain good blood sugars levels.

My pre-workout snack is a low glycemic carb and some lean protein (like sweet potato and chicken) which I eat about an hour before my workout. By eating a low glycemic carb plus some protein, I get enough energy for my workout without having to take a lot of insulin.

My post workout snack consists of a high glycemic carb with an easily digested protein (like a banana and a whey protein shake).

As mentioned, I generally reduce my bolus amount for the pre- and post-workout meals by up to 50%, especially on high-rep and superset days, due to the cardiovascular component of the workout which always makes my blood sugar drop.

How to adjust your insulin up to 36 hours after a resistance workout

My approach to insulin adjustments for the 24-36 hours after I leave the gym is the same no matter what kind of resistance training I’ve done. What happens when you do resistance training is that you create microscopic tears in your muscle fibers, and for the next 24-36 hours, your muscles heal and get bigger and stronger. During this period, your muscles need energy in order to heal and that has to come from somewhere, so low blood sugars can easily be the result if I don’t plan ahead.

If I do resistance training less than four times per week, I will typically have to reduce my nighttime basal insulin by up to 50% on the days on which I work out (this is different for every individual, so you need to experiment and track your results to find what works for you).

If I do resistance training more than four times per week, the increased insulin sensitivity is present all the time and I can simply lower my nighttime basal permanently without having to adjust for individual workouts.


I find it easier to adjust for resistance training than for cardio, as long as I am very aware of the kind of resistance training I am doing and remember these guidelines:

  1. High-rep workouts in which your heart rate is elevated will most likely make your blood sugar drop
  2. Low-rep workouts that don’t elevate your heart rate significantly (like arms or shoulders) most likely won’t affect your blood sugar
  3. Hard low-rep workouts of large muscle groups can affect your blood sugar like an interval workout, potentially leading to an increase in blood sugar
  4. Don’t be scared of eating!!! Eat enough lean protein and carbs to fuel your workout and to ensure muscle recovery
  5. Consider reducing your insulin levels appropriately during the 24-36 hours after a workout to adjust for the type of resistance training you’ve done

Have fun in the gym!