Precautions and Disclaimer: See page bottom.
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Carbohydrates and Blood Sugar
Carbohydrate consumption has a major effect on blood sugar (glucose) levels—often causing a rise—in many people with type 2 diabetes. Most folks with diabetes are taking medications to lower their glucose levels.
Low-carb and very low-carb diets (often called ketogenic diets) restrict the dieter’s carbohydrate consumption rather dramatically.
Remember that the main classes of food—macronutrients—are proteins, fats, and carbohydrates. Common carbohydrate sources are:
- starchy vegetables (e.g., potatoes, corn, peas, beans)
- milk products
- sweetened beverages
- other added sugars (e.g., table sugar, high fructose corn syrup)
The typical American way of eating provides 250–300 grams of carbohydrate daily. Very low-carb diets limit carbohydrates to under 50 grams daily, typically in the 20–25 gram range. Low-carb diets provide 50 to 130 grams of carbohydrate daily. In healthy people and mild diabetics not treated with medication, this carbohydrate restriction rarely causes low blood sugar problems (hypoglycemia). But in other diabetics, carbohydrate restriction can lead to serious, even life-threatening, symptoms of hypoglycemia.
Hypoglycemia is also a potential problem for diabetics on traditional balanced reduced-calorie diets.
Hypoglycemia, however, is an even greater risk for diabetics taking certain diabetic medications while on a carbohydrate-restricted diet.
Hypoglycemia: Recognition and Management
Hypoglycemia is the biggest immediate risk for a diabetic starting a carbohydrate-restricted diet. Hypoglycemia means an abnormally low blood sugar (under 60–70 mg/dl) associated with symptoms such as weakness, malaise, anxiety, irritability, shaking, sweating, hunger, fast heart rate, blurry vision, difficulty concentrating, or dizziness. Symptoms often start suddenly and without obvious explanation. If not recognized and treated, hypoglycemia can lead to incoordination, altered mental status (fuzzy thinking, disorientation, confusion, odd behavior, lethargy), loss of consciousness, seizures, and even death (rare).
Your personal physician and other healthcare team members will teach you how to recognize and manage hypoglycemia. Immediate early stage treatment involves ingestion of glucose or other carbohydrate: six fl oz (180 ml) sweetened fruit juice, 12 fl oz ( 360 ml) milk, four tsp (20 ml) table sugar mixed in water, four fl oz (120 ml) soda pop, candy, glucose tablets or paste, etc. Fifteen to 30 grams of glucose or other carbohydrate should do the trick. Hypoglycemic symptoms respond within 20 minutes.
If level of consciousness is diminished such that the person cannot safely swallow, he will need a glucagon injection. Non-medical people can be trained to give the injection under the skin or into a muscle. Ask your doctor if you are at risk for severe hypoglycemia. If so, ask him for a prescription so you can get an emergency glucagon kit from a pharmacy.
Do not assume your sugar is low every time you feel a little hungry, weak, or anxious. Use your home glucose monitor for confirmation when able. If you do experience hypoglycemia, discuss management options with your doctor: downward medication adjustment, eating more carbohydrates, shifting meal quantities or times, adjustment of exercise routine, etc. Eating at regular intervals three or four times daily helps prevent hypoglycemia. Spreading carbohydrate consumption evenly throughout the day also helps. Someone most active during daylight hours as opposed to nighttime will generally do better eating carbs at breakfast and lunch rather than concentrating them at bedtime.
Diabetics considering or following a low-carb or very low-carb ketogenic diet must work closely with their personal physician and dietitian, especially to avoid hypoglycemia. Clinical experience with thousands of patients has led to generally accepted guidelines.
Diabetics not being treated with pills or insulin rarely need to worry about hypoglycemia. Similarly, diabetics treated only with diet, metformin, colesevalam, and/or an alpha-glucosidase inhibitor (acarbose, miglitol) should not have much, if any, trouble with hypoglycemia. The DPP4-inhibitors (sitagliptan and saxagliptin) do not seem to cause low glucose levels, whether used alone or combined with metformin or a thiazoladinedione.
Thiazolidinediones by themselves cause hypoglycemia in only 1 to 3% of users, but might cause a higher percentage in people on a reduced calorie diet. As of January 9, 2010, I’m not sure if bromocriptine by itself causes hypoglycemia: I suspect not, but check with your own doctor or pharmacist.
People who don’t know the class of their diabetic medication should ask their physician or pharmacist.
Type 2 diabetics are at risk for hypoglycemia if they use the following drug classes
- sulfonylureas: glipizide, glyburide, glimiperide, chlorpropamide, acetohexamide, tolbutamide
- meglitinides: repaglinide, nateglinide
- pramlintide plus insulin
- exenatide plus sulfonylurea
- and possibly thiazolidinediones: pioglitazone, rosiglitazone
Common management strategies for diabetics on these drugs and starting a very low-carb ketogenic diet include:
- reduce the insulin dose by half
- change short-acting insulin to long-acting (such as glargine)
- stop the sulfonylurea, or reduce dose by half
- reduce the thiazolidinedione by half
- stop the meglitinide, or reduce the dose by half
- monitor blood sugars frequently, such as four times daily, at least until a stable pattern is established
- spread what few carbohydrates are eaten evenly throughout the day
Management also includes frequent monitoring of glucose levels with a home glucose monitor, often four to six times daily. Common measurement times are before meals and at bedtime. It may be helpful to occasionally wake at 3 AM and check a sugar level. To see the effect of a particular food or meal on glucose level, check it one or two hours after eating. When eating patterns are stable, and blood sugar levels are reasonable and stable, monitoring can be done less often. When food consumption or exercise habits changes significantly, check sugar levels more often.
If you’re thinking that many type 2 diabetics on low-carb and very low-carb ketogenic diets use fewer diabetic medications, you’re right.
Precautions and Disclaimer: The ideas and suggestions in this document are provided as general educational information only and should not be construed as medical advice or care. Information herein is meant to complement, not replace, any advice or information from your personal health professional. All matters reagarding your health require supervision by a personal physician or other appropriate health professional familiar with your current health status. Always consult your personal physician before making any dietary, nutritional supplement, or exercise changes. Steve Parker, M.D., pxHealth, and Vanguard Press disclaim any liability or warranties of any kind arising directly or indirectly from use of this document. If any problems develop, always consult your personal physician. Only your physician can provide you medical advice.
Last updated January 9, 2010