Before exercise: Check your blood sugar before your workout

Before jumping into a fitness program, get your doctor's OK to exercise — especially if you've been inactive. Ask your doctor how activities you're contemplating might affect your blood sugar. Your doctor can also suggest the best time to exercise and explain the potential impact of medications on your blood sugar as you become more active.

For the best health benefits, experts recommend at least 150 minutes a week of moderately intense physical activities such as:

• Fast walking
• Lap swimming
• Bicycling

Experts also recommend that children — even those with type 1 diabetes — participate in at least 60 minutes of moderate to vigorous activity every day.

If you're taking insulin or other medications that can cause low blood sugar (hypoglycemia), test your blood sugar 15 to 30 minutes before exercising.

If you don't take medications for your diabetes or you don't use medications commonly linked to low blood sugar levels, you probably won't need to take any special precautions prior to exercising. Check with your doctor.

Below are some general guidelines for pre-exercise blood sugar levels. The measurements are expressed in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).

• Lower than 100 mg/dL (5.6 mmol/L). Your blood sugar may be too low to exercise safely. Eat a small snack containing 15 to 30 grams of carbohydrates, such as fruit juice, fruit, crackers or even glucose tablets before you begin your workout.
• 100 to 250 mg/dL (5.6 to 13.9 mmol/L). You're good to go. For most people, this is a safe pre-exercise blood sugar range.

• 250 mg/dL (13.9 mmol/L) or higher. This is a caution zone — your blood sugar may be too high to exercise safely. Before exercising, test your urine for ketones — substances made when your body breaks down fat for energy. The presence of ketones indicates that your body doesn't have enough insulin to control your blood sugar.

  If you exercise when you have a high level of ketones, you risk ketoacidosis — a serious complication of diabetes that needs immediate treatment. Instead of exercising immediately, take measures to correct the high blood sugar levels and wait to exercise until your ketone test indicates an absence of ketones in your urine.