Maxy sez : How Food Affects Your Blood Sugar

By Clifton Jackness, MD

Question : How long after eating does food affect your blood sugar? When is the best time to test my blood sugar in relation to meals?

A: Food is the number one reason for fluctuations in blood sugar, or glucose. Usually, food raises blood sugar while alcohol may lower blood sugar. Depending on what you are eating, blood sugar can rise beyond 300 mg/dl if the food contains sugar or simple carbohydrates. For example, milk and juices are used medically to correct hypoglycemia, or low blood sugar, because they can quickly raise sugars after only drinking 3 to 4 ounces. 

If you are curious about what a particular food or a meal does to your blood sugar, check your glucose level just before you eat, and then check it again two hours after finishing your meal. The American Diabetes Association recommends that a safe postprandial sugar level should not exceed 180 mg/dl. If the sugar is higher than 180 mg/dl and you are taking insulin or medication, you may need to take a higher dose before eating that same meal again or adjust the meal — either by eating less or reducing the carb content.

For people diagnosed with diabetes, it’s very easy to become obsessive about blood sugars and be tempted to check them multiple times throughout the day. But that’s usually not necessary. For example, someone who takes short- or rapid-acting insulin before meals should check sugars before each meal to decide how much to take, and then again at bedtime, which will help their healthcare provider know whether to adjust the daily dose of long-acting insulin. 

When monitoring blood sugar around meals, remember to check it right before the meal and then two hours after eating. Almost everyone — with or without diabetes — may have a high blood sugar while eating or right afterwards, which is why there hasn’t been standardization around what a normal sugar is during meals. It’s crucial to wait at least one to two hours after eating to get an accurate postprandial reading.

Maintaining a balanced blood sugar throughout the day can seem difficult, but it’s actually very doable if you commit to some up-front work for a week or two. I have found from my practice that most people eat the same 20 to 30 foods all of the time, and if they think about it, they can easily recognize patterns and develop schedules based on that. Keeping a food and blood sugar log to track when sugars go up and down will help you figure out what works for you. 

A common issue with keeping blood sugar balanced is eating only two or three large meals a day — which will spike blood sugar when you’re eating and cause dips during the long periods between meals. Splitting up the food into four to six smaller meals can help prevent those swings in blood sugar. 

If on oral medication or a non-insulin injectable for diabetes, ask your doctor about when specifically that medication should be taken. Recent studies on some of the newer diabetes drugs have shown some benefits to taking medications at specific times during the day. 

Being successful in managing diabetes is similar to what it takes to be successful in other aspects of life: organization and regimentation. With today's developments in medications and technologies, the future is bright.