There are many different types of insulin on the market, and they can generally be categorized into two different kinds: basal or bolus. Basal insulin is a "background" insulin which controls blood sugars all day long. Bolus insulin (also called mealtime or prandial insulin) on the other hand, covers blood sugar spikes after eating.
All people with Type 1 diabetes should be using bolus insulin, and some people with type 2 diabetes need bolus insulin as well. People with type 2 diabetes are generally put on basal insulin first, but that’s not necessarily always the case.
To make things confusing, there are different types of bolus insulin, as well as LOTS of different ways it can be prescribed. Rapid-acting insulin is the most common type of insulin prescribed to be used as a bolus. These insulins start working relatively quickly and completely leave the body somewhere around 3-5 hours after injecting. Their quick onset, peak and duration (read here for more information) make them perfect for covering the carbohydrates you eat. Short-acting insulin is also an option, but dosing it can be a little tricky since they have a longer onset, peak and duration. Depending on your insurance coverage though, they may be much less expensive.
So, how much should you take? How many times a day? That depends on a WHOLE lot of factors! It depends on how much you weigh, how insulin resistant you are, your doctor’s comfort level and preferences, your schedule, as well as how much you eat.
Generally, for people with type 1 diabetes, bolus insulin is taken before they eat anything with carbohydrates. An “insulin-to-carbohydrate ratio” is generally provided to determine how much to take. Everyone’s insulin-to-carbohydrate ratio is different and may change over time, or may even be different for various times of day. Let’s use an example to demonstrate: Bob has an insulin-to-carbohydrate ratio of 1:15. This means that he should take 1 unit of insulin for every 15 grams of carbohydrates he consumes. At lunch one day he sits down to a turkey sandwich and a small apple. He determines that his lunch contains 45 grams of carbohydrates, so he takes 3 units of his rapid-acting insulin prior to eating lunch. He will take a different amount of insulin at different meals as not all foods contain the same amount of carbs.
For people with type 2 diabetes, many providers do not prescribe an insulin-to-carbohydrate ratio, although this is the gold standard. Instead, they may tell you to take a certain amount of insulin at each meal. For example, you may be told to take 10 units at breakfast and lunch and then 15 units at dinner. A stepwise approach can also be effective, in which your doctor tells you to take a certain amount of insulin before just one or two meals. For example, you may be told to take 5 units of Novolog before dinner. If your A1C is still not at goal at your next blood test, you then may be told to take a certain amount before, say breakfast, as well. This approach is nice because there are less injections per day. Lastly, you may be instructed to take your mealtime insulin based on your blood sugar reading. This is often referred to as a sliding scale or rainbow coverage. You may be instructed to take the sliding scale by itself or in addition to an insulin-to-carbohydrate ratio or specific number at meals.
Talk to your prescribing provider regarding when to take your bolus insulin, in addition to reading the instructions on the package insert. Generally, it is recommended to take rapid-acting insulin 15 minutes before a meal and short-acting insulin 30 minutes before a meal. Some of my patients struggle with this as the timing is so important. Keeping your insulin supplies with you will be necessary so you can be prepared for eating out or on the run.
If you are having hypoglycemia frequently, talk to your provider as your dose may need to be decreased. Conversely, if you are having a lot of high blood sugars after meals, your dose may need to be increased or possibly prescribed in a different way. If you are taking mealtime insulin, I highly recommend checking your blood sugars about 2 hours after meals, even if it’s just once in a while, to see how your insulin as well as the foods you’re eating are affecting your blood sugars.
If you feel your insulin regimen is confusing or not working for you, there are people who can help! This stuff can get confusing! A Certified Diabetes Educator can sit down with you to explain how all your insulins work and help you come up with a plan to make it all happen. We can also arm you with questions to ask your prescribing provider.
Bolus insulin can be used in combination with basal insulin, as well as oral or other injectable medications. Potential side effects for all insulins include weight gain and hypoglycemia.