“Gary, I think I need more insulin at breakfast.”
“Why do you say that, Julianne?”
“Because I’m always having high readings right afterwards, and my obstetrician said I shouldn’t spike after I eat.”
“And what happens after the spike?”
“It usually comes down to normal before lunch. So do you think I should take more insulin?”
After-meal blood sugar spikes can create quite a quandary for anyone with diabetes, particularly during pregnancy. Research has shown that fetal macrosomia (overgrowth of the baby) becomes more common when post-meal blood sugars exceed 120 mg/dl (6.7 mmol). With post-meal readings above 140 mg/dl (7.8 mmol), the risk more than doubles from baseline.
Fetal macrosomia can cause many problems during pregnancy. When the baby grows and develops too rapidly, it can lead to a premature and more complicated birth. It may also cause injuries to occur to the baby during delivery.
Why do after-meal blood sugars have such a major influence on the baby’s growth? Nobody knows for certain. Perhaps, when the mother’s blood sugar “spikes” suddenly after meals, the baby is fed more sugar than its pancreas can “cover” with insulin, and high fetal blood sugar results. And because the baby’s kidneys spill almost all excess sugar from the baby’s bloodstream back into the amniotic fluid, the baby then drinks in the extra glucose and winds up growing more than it should.
Suffice to say that post-meal blood sugar spikes are something to avoid during pregnancy. But how do we do it? Getting back to Julianne’s question, if she takes more insulin, she’ll probably wind up hypoglycemic before lunch. Luckily, we have some excellent techniques for preventing the after-meal highs without having to take more mealtime insulin.
What Causes Spikes In The First Place?
The reason blood sugar “spikes” very high after eating for most people with diabetes is a simple matter of timing. In a non-diabetic, eating a meal results in the immediate release of insulin into the bloodstream, and production of a hormone called amylin. Insulin produced by the pancreas does its job in just a few minutes. And amylin keeps food from reaching the intestines too quickly (where the nutrients are absorbed into the bloodstream). As a result, the blood sugar rises only a small amount after meals.
However, in people with diabetes, the timing is all fouled up. Rapid-acting insulin that is injected (or infused by a pump) takes approximately 15 minutes to start working, 60-90 minutes to “peak”, and four hours or more to finish working. And in people with diabetes, amylin is either produced in insufficient amounts or not at all. As a result, food digests even faster than usual. This combination of slower insulin and faster digestion can cause the blood sugar to rise very high right after eating.
Measuring the Spikes
On average, the blood sugar hits its high point about one hour and 15 minutes after starting a meal. So checking your blood sugar (using a finger stick) about an hour after eating should provide a good indication of how much of a spike is taking place. Check before and after breakfast, lunch and dinner several times to determine how much of a spike is taking place. Or better yet, wear a continuous glucose monitor and observe the trend graphs for a few hours after eating to see how high your blood sugar gets before it starts its downward decent.
The goal during pregnancy is to keep the blood sugar as close to normal as possible without frequent or severe hypoglycemia. In general, keeping the blood sugar below 140 mg/dl (7.8 mmol) at the post-meal peak greatly reduces the risk for fetal macrosomia. What’s more, it can be achieved safely… without cranking up the insulin dose.
Spike Reduction Techniques
To reduce the post-meal blood sugar rise, a number of strategies can be used:
1. Choose the right insulin (or medication)
Insulins that works quickly and for a short period of time will work better at controlling after-meal blood sugar than those that work slowly over a prolonged period of time.
Rapid-acting insulin analogs, which start working 10-15 minutes after injection and peak in about an hour, will cover the post-meal blood sugar rise much better than Regular insulin which takes 30 minutes to begin working and 2-3 hours to peak. Lispro (Humalog) and aspart (Novolog/NovoRapid) are considered safe for use during pregnancy. No increased risk of congenital malformations or immune responses has been found with these types of insulin.
If you use a morning injection of NPH (cloudy) insulin to “cover” the carbs eaten in the middle of the day, your post-meal blood sugar is likely to be very high. This is also the case if you take a premixed insulin (75/25, 70/30 or 50/50) twice daily. Instead, consider taking rapid-acting insulin before each meal/snack, and talk to your doctor about your various basal insulin options.
2. Back Up Your Bolus
For those taking rapid-acting insulin at mealtimes (boluses), the timing of the insulin can have a huge impact on the after-meal spikes. Boluses given too late can produce significant highs soon after eating, whereas a properly timed bolus can result in excellent after-meal control.
Unless you suffer from gastroparesis (a nerve disorder that slows emptying of the stomach), it is best to give boluses before eating. How long before? It depends… mainly on what your blood sugar is prior to the meal. The higher your blood sugar, the earlier the bolus should be given. With a pre-meal blood sugar that is above-target, it is best to give the bolus and then wait about 30 minutes before eating. Near your target? Wait 15 minutes. Below target? Either take the bolus and eat right away, or take the bolus after eating. The obvious exception to this rule is during those phases of pregnancy when you may not know if your meal is going to “stay down”. If you are susceptible to vomiting, wait until after you are reasonably sure that your food will stay down before bolusing.
Does earlier bolusing make a difference? Absolutely. Research has shown that simply giving mealtime boluses before eating rather than after can reduce the post-meal spike by about 50 mg/dl (2.8 mmol).
3. Bolus for the Basal
In order to have more insulin working right after eating and less working several hours later, a pump user can run a substantial temporary basal reduction for 3 hours just before eating and give a normal bolus equal to the basal insulin that would have been delivered. For example, if your basal rate in the morning is .6 units per hour, you could bolus an extra 1.8 units before breakfast and set a temporary basal rate of 10% (90% reduction), for the next 3 hours.
4. Think Lower GI
Glycemic index (GI) refers to the speed with which food raises the blood sugar level. While all carbohydrates (except for fibre) convert into blood sugar eventually, some forms do so much faster than others.
Many starchy foods (breads, cereals, potatoes, rice) have a high GI; they digest easily and convert into blood sugar quickly. Some starchy foods (pasta, beans, peas) have lower GI values. Foods that have dextrose in them tend to have a very high GI. Table sugar (sucrose) and fructose (fruit sugar) have moderate GI values, while lactose (milk sugar) is slower to raise blood sugar. A number of books, such as Dr. Jennie Brand-Miller’s Glucose Revolution series, contain extensive information about the glycemic index, along with lists of GI values for hundreds of foods.
As a general rule, switching to lower-GI foods will help to reduce your after-meal blood sugar spikes. There are certain characteristics/properties that slow down the rate at which foods raise blood sugar. For instance:
- High-fibre foods digest slower than low-fibre foods
- Hi-fat foods digest slower than low-fat foods
- Solids digest slower than liquids
- Cold foods digest slower than hot foods
- Under-ripe and under-cooked foods digest slower than over-ripe/over-cooked foods
- Whole/natural foods tend to digest slower than processed foods
Another unique food property that affects rate of digestion is acidity. This is why sourdough bread has a much lower GI value than regular bread. Research has shown that adding acidity in the form of vinegar (straight or in dressing/condiment form) can reduce the one-hour post-meal blood sugar rise by 50% or more.
Below are some examples of ways to substitute typical high-GI foods for lower-GI options:
5. Split your meal
To keep your blood sugar from rising all at once, consider saving a portion of your meal for a “snack” one or two hours later. Still give the full mealtime insulin before eating any of the meal; just don’t eat all of the food at once. For example, if you have a bowl of cereal and juice for breakfast, considering having the cereal at breakfast time, and postpone the juice until mid-morning. Just don’t forget to eat the rest of the meal later on, or your blood sugar could drop very low.
6. Get Moving!
Physical activity after eating can reduce post-meal spikes in a number of ways. If insulin was taken prior to the meal or snack, the enhanced blood flow to the skin surface is likely to make the insulin absorb and act more quickly. Muscle activity diverts blood flow away from the intestines, resulting in slower absorption of sugars into the bloodstream. Plus, the sugar that does enter the bloodstream is likely to be “consumed” by the working muscles.
How much activity is required to experience these benefits? Not much. Ten or 15 minutes (or more) of mild activity will usually get the job done. The key is to avoid sitting for extended periods of time after eating. Instead of reading, watching TV or working on the computer, go for a walk, work outside, or do some chores. Try to schedule your active tasks (housework, yardwork, shopping, walking pets) for after meals. Also attempt to schedule your exercise sessions for after meals.
7. Prevent Hypoglycemia.
How’s that? Prevent lows to prevent highs? It’s true. One of the body’s responses to hypoglycemia is accelerated gastric emptying: food digests and raises blood sugar even more rapidly than usual. This is understandable: we want the blood sugar to rise as quickly as possible when we’re low. But being low before meals will definitely contribute to an excessive post-meal spike.
Note: Gary Scheiner MS, CDE is owner and clinical director of Integrated Diabetes Services, a private practice specialising in blood glucose regulation and advanced self-management training for people who utilise intensive insulin therapy. He is both an exercise physiologist and a Certified Diabetes Educator. One of the specialties of his practice is pregnancy and type-1 diabetes. He and his staff of CDEs offer their services remotely via phone and the internet for clients throughout the world. A devoted husband and father of four, Gary has had type-1 diabetes for 28 years and makes extensive use of both pump and CGM technology. For more information, contact him at firstname.lastname@example.org, or call him in the US: 877-735-3648, or outside the US: +1-610-642-6055.