Every time I eat I am trying to replicate a complex bio-chemical process using inaccurate measuring tools, a dangerous drug, and complex calculations where even the constants ebb and flow. This is done without medical supervision and with less training than is required to get a basic CPR certification. When I get it wrong, I pay the physical and emotional price, not to mention criticism (or benignly condescending scorn) from people who have no clue what all is involved.
With Type 1 Diabetes, the body cannot identify changes in blood glucose (BG). It cannot secrete insulin to cover for food consumed in a meal. It cannot secrete extra insulin to keep the BG at normal levels. These are things that I have to do for myself. I count carbohydrates I'll consume and calculate how much insulin will be necessary. I also calculate how much insulin is needed to keep my blood glucose in normal range and then inject that.
Too much insulin leads to an always annoying (frequently painful/terrifying) and potentially fatal condition called hypoglycemia. This happens to me as many as 2 or 3 times a day, while I can sometimes make it a whole week without this happening.
Too little insulin leads to high BG, or hyperglycemia. If it happens too much for too long, it can lead to complications like blindness, kidney failure, amputations, nerve damage or cardiovascular disease. If it gets way too high, acid levels can build to dangerous and potentially fatal levels in a condition called diabetic ketoacidosis (also called a diabetic coma).
1. Calculate Correction Insulin Dose
Before a meal, I test my Blood Glucose (BG). I try to keep it between 90-120 mg/dl. If it is low, I'll use less insulin and let some of the carbohydrates in the meal bump it up to that target. If I am high, then I'll add extra insulin to push my BG down.
Example: my BG before the meal is 286. My goal is 90-120. To have a target for the calculation I'll use 105. I need 1 unit of insulin to move my BG down 50 mg/dl. This is called the 'correction factor.' I subtract 105 (the target) from 286 (my actual BG) which yields 181. I divide that by the correction factor, or 186/50=3.72. To move my BG down to my target, I'll need to inject 3.7 units.
With my insulin pump, the BG from the test is transmitted wirelessly from the meter to the pump. The pump knows my correction factor (which is different at different times of day). When I tell the pump to inject insulin for this meal, it will automatically calculate the correct amount of insulin.
If using insulin injected by a syringe or a pen device, I have to calculate this on pencil and paper. Some phone apps can do it, but with a pump I've never felt a need to use one.
2. Calculate Insulin Dose for the Meal
Deciding what to eat depends on one thing: data. Picking tasty things is secondary, since I must have nutritional information (specifically carbohydrate content) to properly compute insulin dosage. Ideally, I avoid meals with over 100 grams. That requires a large dose of insulin, and in my experience the larger the dose, the more unpredictable the results.
Here is how it works, using a dinner at home as an example.
My menu for dinner is:
TV dinner: 58
The total 'carb count' for this meal is 109.5.
Since it is above my self-imposed target of 100, I'll skip the milk. Instead, I might have something with 0 carbohydrates, i.e.: Diet Coke, a Diet Snapple, water, etc. My new 'carb count' is now 85.5 grams of net carbohydrates.
Now I must calculate how many units of insulin I will need for this meal. This number, called the 'carbohydrate ratio.' If I have the meal between midnight and 8:00 a.m. I need 1 unit for every 15 grams. From 8:00 until 5:00 p.m. I'll need 1 unit for every 16 grams. After 5:00, it again changes, this time to 1 unit for every 12 grams.
Since I am eating after 5:00 p.m. I will inject one unit of insulin for every 12 grams of net carbohydrates. So 85/12=7.1 units of insulin. I round the 85.5 down to 85 since the insulin pump only accepts whole numbers.
Because I use an insulin pump, it can calculate insulin required. The carbohydrate ratio is stored in the pump's memory, but I need to tell it how many grams of net carbohydrates in the meal.
Next: put it all together.
3. Administer the Total Insulin Dose and Additional Considerations
My correction dose for this meal is 3.7 units. To account for the meal, I will also need 7.1 units. The total dose for this meal is 10.8 units.
I will inject this using my insulin pump.
When I tested my BG before the meal, my insulin pump calculated then correction dose of insulin for me.
Before I eat the meal, I need to tell the pump that I am going to need an injection of insulin to cover the food I am about to have. This is called a 'bolus.'
I use a feature of the pump called a 'bolus wizard.' It takes the BG test results and calculates the correction dose. It then asks me how many net carbs I will eat. I enter 86 grams (the 85.5 rounded up).
The insulin pump calculates that in total I will need 3.7 plus 7.0 units, or 10.7 total.
Next it asks me if I want it injected all at once, a portion initially and the rest over an extended period of time, or the entire dose over an extended period of time.
Normally, you want the correction all at once. For the meal, it depends. For me, I have gastroparesis, which means my stomach does not digest and empty food properly. This is a complication of diabetes. It is unpredictable, cannot be felt of measured, so In have to guess. After months of trial and error, my endocrinologist and I have decided that 30% of the meal dose should bolus all at once, and the remainder over 1 hour. It doesn't work very well, but it works better than everything else we have tried.
I never, ever, not once administer the bolus until the meal is sitting in front of me. If something goes wrong I'll have to scramble to get additional carbs to counteract the insulin dose. That is difficult and potentially dangerous.
If eating out, I stick to chain restaurants if possible. Nutritional data is often available from the establishment, or I use an app called 'Calorie King.' If it isn't a chain, and the menu if fairly pedestrian, I can use the app to approximate the carb count. If it has an esoteric menu (something I always check before eating out) then I'll give an excuse to do something else.
Sometimes, particularly in a hospital setting, I have no choice but to eat without getting a carb count. Then I do the best I can, making sure to monitor my BG carefully after the meal to avoid going below my target.
DIABETES LIFESTYLE CHANGES
First, between snacking is a problem. If it has carbs, there is a possibility that the insulin for a meal and additional insulin for a snack could 'stack' or have a big impact that sends my blood sugar dangerously low. For the first 15 years I had diabetes and used a syringe and paper calculations, I quit having snacks with carbs to avoid this. It is possible to snack with an insulin pump since it can account for the active insulin from the meal, but I generally don't bother. If I do, it is something with no carbs, i.e.: pickles, some vegetables, meat, etc.
I usually do all of this quietly, without drawing attention to what I am doing. It is socially awkward and makes people uncomfortable. Nobody wants to see blood at the dinner table, or be feel guilty at the gymnastics I have to go through before a meal. I'll do the BG test and pick the menu items based on how likely I can do a carb count accurately before the meal. When it arrives, I do the carb count and enter the data into my pump and start the bolus. If somebody does notice, usually a friend, at most they think 'he's doing his diabetes thing.' They have no clue unless I've talked them through everything I am doing and the reason why. That has happened maybe once or twice. Most folks get lost and confused pretty early in the process.