If you have diabetes, pre-diabetes or insulin resistance, then you’ve heard your doctor tell you over and over that you need to exercise daily to stay healthy. You may be sick of hearing it, but he’s telling you for a reason. Exercise increases insulin sensitivity so your body is able to use blood glucose more effectively, and it lets your body utilize the glycogen stored in the liver to feed your body’s cells without the need for insulin. Exercise also wards off obesity and cardiovascular disease, which are hallmarks of type 2 diabetics.

All of this is good, but there’s a catch.

Exercise—especially when it’s prolonged or strenuous—can cause hypoglycemia. High blood glucose levels have a cumulative effect that can eventually cause serious damage to your eyes, your heart and other vital organs, but hypoglycemia (read: low blood sugar) can cause critical health problems right away. If left untreated, it can quickly cause seizures, coma and even death.

That may sound like pretty serious stuff, but it really is.

When you exercise strenuously, your body works diligently to use up your blood glucose and glycogen to provide fuel to the muscles so you can keep up with your pilates class or keep on running those touchdowns. When you stop exercising, this process doesn’t stop right away. That’s why it can take from four to 24 hours for your body to rebuild its stores of glycogen.

You’re probably fine if you’re taking the dog for a walk or playing nine holes of golf, but if you’re planning on running a marathon or playing a soccer or football game, there are some precautions you should take:

  • Avoid any alcohol consumption before or after you exercise and don’t jump into the hot tub or sauna, as both can lower your blood glucose levels even more. (Yes. That means no beers with the guys right after the ball game.)
  • Plan your exercise routine for at least two hours before bedtime to avoid the risk of hypoglycemia setting in when you’re sleeping an unaware of the symptoms.
  • Eat up to 15 grams of complex carbohydrates before and after your exercise routine, and add up to 8 grams of protein if you don’t have a meal scheduled within an hour of the exercise.
  • Check your blood glucose before and after exercising so you can catch decreasing blood glucose levels before you feel the symptoms.

Before you start any new exercise routine, talk to your doctor or nutritionist to get the skinny on how and when you should change your meal schedule or insulin intake. Exercise is a necessary part of your overall health routine, but there’s a bit more to it than just getting up and going for a jog.