Diabetes Mellitus: Diet, Exercise, & Medication
Patients with type 1 diabetes should use carbohydrate counting or the carbohydrate exchange system to match insulin dose to carbohydrate intake. For example, if a carbohydrate-to-insulin ratio of 15 grams to 1 unit is used, the patient will require 1 unit of rapid-acting insulin for each 15 g of carbohydrate in a meal. These ratios must be tailored to each patient.
Patients with type 2 diabetes should restrict calories, eat regularly, increase fiber intake, and limit intake of refined carbohydrates and saturated fats. However, all diabetic patients, including pregnant patients with gestational diabetes, may find that carbohydrate counting or exchange is helpful in regulating their blood sugar. The carbohydrate intake for most people should be 45 to 65% of total calories for the day. People on low-calorie diets and those who are physically inactive may need to aim for the lower end of that range. One gram of carbohydrate provides about 4 calories. Here’s an example – if the patient is on an 1,800 calorie diet and wants to get 50% of those calories from carbohydrates, they should aim for about 225 grams of carbohydrate daily. (50% x 1,800 calories = 900 calories 900 calories 4 = 225 grams of carbohydrate)
The carbohydrate intake should be spread out throughout the day, and based on weight, activity level, medicines, and blood glucose targets. It is important to teach the patient how to read nutrition labels and estimate the amount of carbohydrates in foods they typically eat. For example, the following foods each contain about 15 grams of carbohydrate – 1 slice of bread, ⅓ cup of rice or pasta, ½ cup fruit or fruit juice, ½ cup pinto beans, ½ cup of starch vegetables such as mashed potatoes or corn, and ¾ cup of dry cereal. Also, the internet has helpful carbohydrate counting tools that let you enter a type of food and find out what nutrients the food contains, including carbohydrates.
In all persons with diabetes, physical exercise is important to achieve and maintain a healthy weight, and should increase gradually to whatever level a patient can tolerate. Both aerobic and resistance exercise have been shown to improve blood glucose control. Exercise works as an insulin sensitizer, enhancing glucose uptake into skeletal muscle, occurring in both type 1 and type 2 diabetes. Patients who experience hypoglycemic symptoms during exercise should test their blood glucose and eat a carbohydrate or lower their insulin dose as needed to get their glucose slightly above normal just before exercise. Exercise should be done on a regular basis, except for during periods of hyperglycemia (blood sugar >250) and ketosis. The combination of hyperglycemia, ketosis, and exercise exerts a physiologic stress on the body, resulting in further elevation of blood sugar. Each patient should have a complete history and physical exam prior to beginning an exercise routine. Studies have repeatedly shown that physical fitness is a major predictor of survival in individuals with and without diabetes.
Now let’s look at the medication used to treat diabetes. Type 1 diabetes is characterized by absence of insulin, therefore insulin replacement is the first mode of management. Patients with type 2 diabetes sometimes take insulin along with oral medication or by itself. Insulin is a naturally occurring hormone secreted by the pancreas that helps the body use glucose for energy. All insulin available in the United States is manufactured in a lab, but animal insulin can still be imported for personal use. Human insulin is derived from DNA technology, with a strength of U-100 (100 units of insulin per mL of volume). Insulins differ in their speed of onset (how fast it reaches the bloodstream), the peak (when it is at maximum strength), and duration of action (how long it continues to work). The types of insulin include rapid acting, regular or short-acting, intermediate acting, and long acting. Rapid-acting insulin begins to work about 15 minutes after injection, peaks in about 1 hour, and continues to work for 2 to 4 hours. Examples of rapid-acting insulin include Apidra, Humalog, and NovoLog. Regular or short-acting insulin usually reaches the bloodstream within 30 minutes after injection, peaks in about 2 to 3 hours, and is effective for about 3 to 6 hours. Examples of regular or short-acting insulin include Humulin R and Novolin R. Intermediate-acting insulin generally reaches the bloodstream about 2 to 4 hours after injection, peaks 4 to 12 hours later, and is effective for 12 to 18 hours. An example of intermediate-acting insulin is NPH (also known as Humulin N or Novolin N). Intermediate-acting insulins are a cloudy insulin solution. Long-acting insulin reaches the bloodstream several hours after injection and tend to lower glucose levels fairly evenly over a 24 hour period. Examples include Levemir and Lantus.
Premixed insulin can be helpful for patients who have trouble drawing up insulin out of two bottles and reading correct dosages. For example, 1 unit of Humulin or Novolin 70/30 provides 0.7 units of NPH insulin and 0.3 units of regular insulin. A disadvantage of the premixed insulins is that they do not allow for fine tuning of the insulin regimen. Diet and activity must be coordinated with insulin intake so that insulin is available for metabolism when food is absorbed, and food must be available while insulin is acting to prevent blood sugar from dropping too low.
Patients with type 1 diabetes usually start with 2 injections of insulin per day of 2 different types of insulin, generally progressing to 3 to 4 injections per day of insulin of different types. Studies have shown that 3 to 4 injections per day give the best blood glucose control and can prevent or delay the eye, kidney, and nerve damage caused by diabetes. Some patients with type 2 diabetes may need one injection per day without any oral medication, or some may need a single injection of insulin in the evening along with oral medication. Sometimes oral medication stops working and patients start 2 injections per day of 2 different types of insulin, possibly progressing to 3 to 4 injections of insulin per day.
Most often, insulin is given with an insulin syringe, but some patients use an insulin pen or insulin pump. Insulin pens contain a cartridge pre-filled with insulin, with the dose dialed on the pen and injected through a needle. Insulin pumps allow diabetes to be managed by delivering insulin 24 hours a day through a catheter placed under the skin. Insulin is either delivered at a basal rate (steady, continuous dose), or a bolus dose, given around mealtime at the patient’s input. This delivery system most closely mimics the body’s normal release of insulin throughout the day. When insulin is administered by syringe, it must be given with an insulin syringe which has the proper dose measurements. In the hospital, the correct dose should be double checked by two nurses. For home use, the patient should be taught how to administer the correct dose, timing, and site rotation. Insulin enters the blood at different speeds when injected at different sites. Insulin injections are given subcutaneously, and they work the fastest when given in the abdomen, a little more slowly from the upper arms, and even more slowly from the thighs. The injection sites should be rotated, such as rotating the four abdominal quadrants, to avoid hard lumps or extra fatty deposits from developing.
For many patients with type 2 diabetes, glucose levels can be adequately controlled with lifestyle changes and non-insulin antihyperglycemic drugs, but when glucose levels remain out of control with 3 or more drugs, insulin should be added. Oral antihyperglycemic drugs are a mainstay of treatment for type 2 diabetes and work in 4 major ways.
Insulin secretagogues stimulate the pancreas to produce more insulin, and include sulfonylureas (such as glyburide) and meglitinides (such as rePAGlinide).
Insulin sensitizers do not affect the release of insulin but increase the body’s response to insulin. They include biguanides (such as metformin), and thiazolidinediones (such as Avandia and ACTOS). Metformin is the first line drug of choice for treating type 2 diabetes, is most commonly prescribed, and is very effective in reducing the hemoglobin A1c.
Some drugs delay absorption of glucose by the intestine and include alpha-glucosidase inhibitors (such as Acarbose and Miglitol).
Some drugs increase glucose excretion in the urine and include sodium-glucose co-transport-2 inhibitors (such as canagliFLOzin and dapagliFLOzin).
There is another group of drugs that both stimulate the pancreas to produce more insulin and delay the absorption of glucose by the intestine, by increasing glucagon-like peptide 1 (GLP-1). These are the dipeptidyl peptidase-4 (DPP 4) inhibitors, such as sitagliptin and saxagliptin.
Since these drugs act in different ways to lower blood glucose levels, they may be used together. Many different combinations can be used to improve blood glucose control.
So, this is just a brief overview of the oral medications, insulin, and lifestyle changes that are necessary for the treatment of diabetes.
Let’s look at a question for review –
Your patient has a blood glucose level of 240 mg/dL before lunch. You administer 5 units of NovoLog insulin subcutaneously at 11:30. You know that the patient is most at risk for hypoglycemia at what time?
If you answered B, 12:30, you’re correct! 12:30 is one hour after the insulin was administered, and Humalog is a rapid-acting insulin. You know that rapid-acting insulin begins to work about 15 minutes after injection, peaks in about 1 hour, which is when he is most at risk for hypoglycemia, and therefore, should eat lunch right after the insulin was given.
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