Patients frequently want to know “what causes my blood sugars to go up and down even though I am doing the same things every day.” Patients will eat similar foods in the same quantities daily and hope their blood sugars will stay at the same level. Although eating does have a huge impact on blood sugars, there are other causes as well. Let’s look at some of the other possible reasons why your blood sugars may vary from day to day.

Illness or Physical Stress

Having a urinary tract, lung, or skin infection, as well as the flu or gum disease can make your blood sugars fluctuate. Often patients do not realize there is an underlying infection until their blood sugars soar. If you see your blood glucose numbers climbing for no apparent reason you should take your temperature and check with your physician to rule out possible infection. Chronic unrelieved pain or fibromyalgia may also cause blood sugar changes. Find ways to resolve these issues by researching physical therapy, chiropractic medicine, acupuncture, yoga, pain relievers or any other alternative ways to achieve pain relief. Lack of sleep or poor quality of sleep can result in chronic stress and insulin resistance, which will raise blood sugars.


Medications can have an effect on blood sugar variations from day to day. Patients who skip their daily diabetes medicines will have blood sugar fluctuations. Starting new medications can cause changes. Remember, it may take new medications between 4-8 weeks to show improved and consistent blood sugar control. Existing medicine dosages that are increased or decreased will have an impact on sugars. Certain patients do not take medications as prescribed. For example Glipizide (an oral sulfonylurea) needs to be taken 30 minutes prior to a meal. This gives it time to enter your system and squeeze the insulin from the pancreas; otherwise you may not get adequate results.

Some patients may know about proper timing of medication but do not follow protocol. They are often in a rush to eat and move on with the day; they take all their pills at the same time. Know if your medication needs to be taken with food or not. You should know the difference between the types of insulin and the timing. If you take rapid acting insulin (Novolog / Humalog), you should eat within 15 minutes or you may suffer from hypoglycemia. Taking rapid insulin an hour after a meal may cause an initial jump in blood sugars (due to the food) followed by a rebound low. Site rotation and rotation of insulin injections can also be the reason for blood sugar swings.

Patients may repeatedly stick the same spot either because they think it will hurt less (callus formation) or because they are unaware of the need to rotate within a site. After several injections in one quadrant a patient may develop hard lumps, indentations or thick skin. This can prevent proper insulin absorption and result in poor blood sugar management. Changing the site selection from day to day may result in blood sugar variations. Insulin is best absorbed in the abdomen because it is quick and consistent. Using alternative sites including the arm, leg and buttock will possibly cause swings due to absorption rates. When using an insulin pen you should always remove the used needle after your shot and only replace it with a new one at the time of the next injection; otherwise the insulin in the pen could leak and be ruined; this will cause variations in sugar readings. Most insulins only last for 28 days, so expired insulin can cause blood sugar variations.

If your prescription calls for a medication to be taken twice a day, you should not skip a dose or you will have blood sugar fluctuations. Set a timer or place it on the table if you have trouble remembering your second dose. Always check tubing, tape and site placement when using an insulin pump. Make sure you are getting adequate insulin from your pump to prevent blood sugar fluctuations.


Mental stress can cause blood sugar variations. Try to avoid it, learn to say no, meditate, count to 10, exercise, find a hobby, volunteer, see a therapist or make a list on how to reduce stress. Everyone has stress, but learning how to handle and cope with it will help you improve your blood sugars and keep them steady.

Change in Portion Sizes or Total Carbohydrates

If you are following a portion control eating plan and you suddenly change it for a celebration, night out, holiday party or trip you may notice fluctuations in your sugar. If you skip, delay a meal or delete carbohydrates completely you will have variations in your sugar which could be dangerous. Never skip meals.

Sugar Free Soda or Drink Intake

Diabetes Care published a small study stating that “too much diet soda can increase blood sugars even though it is sugar free.” Sugar free soda is extremely sweet and one theory is “it causes you to crave more sweets which may increase weight and blood sugars.” Check with your healthcare provider and use sugar free products in moderation.

These are just a few reasons why your blood sugars vary from day to day. It can be frustrating but if you know what causes blood sugar changes you can make a difference! Look for more in Part 2 of “Why blood sugars swing high or low.” Stay informed!

NOTE: Consult your doctor first to make sure my recommendations fit your special health needs.

Roberta Kleinman

Roberta Kleinman

Roberta Kleinman, RN, M. Ed., CDE, is a registered nurse and certified diabetes educator. She grew up in Long Island, NY. Her nursing training was done at the University of Vermont where she received a B.S. R.N. Robbie obtained her Master of Education degree, with a specialty in exercise physiology, from Georgia State University in Atlanta, Georgia.

She is a member of the American Diabetes Association as well as the South Florida Association of Diabetes Educators. She worked with the education department of NBMC to help educate the hospital's in-patient nurses about diabetes. She practices a healthy lifestyle and has worked as a personal fitness trainer in the past.

She was one of the initiators of the North Broward Diabetes Center (NBMC) which started in 1990 and was one of the first American Diabetes Association (ADA) certified programs in Broward County, Florida for nearly two decades. Robbie has educated patients to care for themselves and has counseled them on healthy eating, heart disease, high lipids, use of glucometers, insulin and many other aspects of diabetes care. The NBMC Diabetes Center received the Valor Award from the American Diabetes Center for excellent care to their patients. Robbie has volunteered over the years as leader of many diabetes support groups.
Roberta Kleinman

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