Medications and Low-Carb Diets

You hear it again and again: "Before you start a new diet or exercise program, check with your doctor." How many people follow this advice? Very few. But there are some situations where getting medical assistance is very important when going on a low-carb diet. If you are taking certain medications, it can be vital for your healthcare providers to be aware of your diet change, because dosages of medication might have to be adjusted or eliminated, or a change of medication might be in order. This is particularly true if you are being treated for diabetes or high blood pressure.

Anyone taking insulin is aware of the direct relationship between the amount of carbohydrate eaten and the amount of insulin required. Large changes in the amount of carbohydrate in the diet should be made only with close coordination of your physician and/or dietitian. A low-carb diet will require less insulin, pure and simple, and it's vital to match the two. One advantage of low-carb diets for insulin-dependent people with diabetes is what Dr. Richard Bernstein calls "The Law of Small Numbers." That is that the less carbohydrate a person eats, the less variation in blood glucose, and the easier it is to control.

On the other hand, when eating larger amounts of carbohydrate there is more variation. For example, a cup of cauliflower might have 3 grams of effective carbohydrate "by the books," but you can never know exactly how much carb there is because all the numbers are averages. You might be getting 2 or 4 grams or even 5 or 6 grams of carbohydrate in your particular serving of cauliflower. Compare that to a medium-sized baked potato. The charts say it will have 32 grams of effective carb, but that potato is going to have a much broader range of possibilities. According to the exact size and variety, it could vary from perhaps 22 to 45 grams. That will make a real difference in the amount of insulin you need, so your blood glucose could go too high or too low more easily.

There are many other medications for diabetes (particularly Type 2 diabetes) which are intended to help control blood glucose. Glucophage (metformin), Avandia (rosiglitazone), Januvia (sitagliptin phosphate) and many others are used for this reason.

If you have been eating a higher-carb diet and switch to low-carb one, you will likely need to adjust your medications. Many people on low-carb diets find that over time they can control their blood glucose with diet and exercise alone and can stop taking the medication. Continuing to take the same dosage could result in hypoglycemic episodes. Even medications such as metformin, which is not supposed to cause hypoglycemia, have been known to have this effect in some people when they change their diets. Again, you must work with your physician to do this safely.

High blood pressure often at least partly corrects with a low-carb diet, sometimes very quickly. The problem is that if a person is already taking medication to lower blood pressure, it can go too low, and this can happen within days of starting a low-carb diet.

Dr. Mary Vernon tells this story: Someone she knew from work, who she knew had high blood pressure, asked her one day if low-carb diets are safe. She said, "Yes, but do it with my supervision." Unfortunately, the man did not follow her instructions. Sometime later, he called her from the floor of his living room. He couldn't stand up without passing out. He was taken to the emergency room, where she met him. His blood pressure was alarmingly low. It turned out he was taking quite a lot of medication to lower his blood pressure, much of which was no longer needed.

Medication for diabetes and high blood pressure are the main ones which may need adjusting if you reduce the carbohydrates in your diet. However, it is always a good idea to talk to your doctor before changing your diet, especially if you have a chronic disease or condition, or are taking medications.