Nine reasons your blood sugar can go up

Diet is the primary way diabetics control the level of sugar in our blood. Doing so, however, is not simple. Here are 9 reasons why blood glucose levels can increase.

In order to prevent type 2 diabetes destroying our bodies, we diabetics need to control the glucose floating around in our bloodstream. Many of us are succeeding in doing so by the diets we eat.

Sometimes however our diets do not work very well and our blood sugar readings rise for reasons we cannot fathom easily. This may be because of a lack of knowledge of how certain foods or other things can affect the level of glucose in our blood.

Here are 9 typical reasons why our blood sugar can rise unexpectedly:

  • caffeine
  • sugar-free food
  • fat-heavy food
  • bagels
  • sports drinks
  • dried fruits
  • a bad cold or flu
  • stress
  • steroids and diuretics

Drinking coffee, black tea, green tea, and energy drinks, all containing caffeine, has been associated with a small, but detectable rise in blood sugar levels, particularly after meals.

This can happen, even if you drink black coffee with zero calories. Two to three cups a day (250mg of caffeine) can have this effect.

In one experiment conducted on 10 people with type 2 diabetes, the subjects were given capsules of caffeine (the equivalent of four cups), rather than coffee. This increased their blood glucose levels by up to 8%. But how caffeine raises blood sugar has not been figured out yet.

The irony is that coffee, both caffeinated and decaffeinated, has other components that reduce blood glucose, and coffee has been associated with a reduced risk of developing type 2 diabetes.

Each person reacts differently to drinks containing caffeine, so it’s best to track your own responses to this little kicker and figure out for yourself whether the effect of caffeine on your blood glucose levels is significant. If it is, you need to cut down or quit.

Sugar-free food

Strange to say, food that is labelled ‘sugar free’ may raise your blood glucose levels. This is because it can contain lots of carbohydrates from starches and fibres.

The only way to find out if a particular food will raise your blood sugar is to check the total carbs figure on the label.

You should also check to see whether the food contains sweeteners such as sorbitol or xylitol. Although these two sugar alcohols add sweetness with fewer carbs than sugar, they can still deliver enough carbs to raise your blood glucose levels.

Fat-heavy Food

Eating food with lots of fat in it will cause the blood glucose levels of type 2 diabetics to rise over time.

When you have this type of diabetes, fat is blocking the receptors in your muscle cells and preventing insulin from doing its job of getting the glucose in your blood stream into the cells.

You can ‘reverse’ your diabetes by unblocking those receptors. The only way to do this is to eat a diet that is very low in fat.

You can best keep fat out of your food by eating a plant-focused diet. You need to avoid all animal products other than the leanest of lean meat. You also need to totally avoid eggs and dairy products, and use as little oil as possible when cooking. Your focus should be on fresh produce, raw or boiled.


Bagels are either no-fat or low-fat which sounds like a good thing if you are a type 2 diabetic and are trying to unblock the receptors in your muscle cells in order to improve you insulin sensitivity.

The problem is that bagels are packed with carbohydrates and calories. In fact, a bagel has more carbs than its equivalent weight in bread. Both bagels and bread are made from highly refined flour which means that they are digested quickly and cause huge spikes in insulin.

Thus you should avoid bagels, just as you avoid white bread, with the possible exception of bagels made from whole-grain flour.
Sports drinks

Sports drinks are designed to help you replenish fluids quickly after exercise. Indeed it is important to prevent dehydration and replace electrolytes you lose by sweating when you are exercising.

The problem is that most sports drinks contain as much sugar as a bottle of lemonade or other soda.

Depending on the brand, the number of calories in 2 fluid ounces (60ml) of a sports drink can vary from 50 to 100, while the carbs can range from 14 to 25 grams. Thus, just drinking one 8-oz bottle means you’ll take in at least 200 calories and well over 50 grams of carbohydrate.

This you don’t need … unless you are training hard for a marathon.

For a moderate workout of less than an hour, plain water will replace what you have lost through perspiration.

But if you do decide to follow fashion and use sports drinks, check the labels carefully for calories and carbs.

Dried fruits

Dried fruit is just as good for you as fresh fruit for a snack. The only problem is that, as the water has been removed, you tend to eat more than you would of fresh fruit.

There are two ways in which fruit can be dried. In the traditional method, drying is undertaken either in the sun or in special heated wind tunnels. Fruits dried in the traditional manner will have virtually the same nutrients as their fresh originals.

In the second method, fruits (such as cranberries, blueberries, cherries, strawberries and mangoes) are infused with a sweetener (often sucrose syrup) before drying. Fruits dried this way will naturally contain much more sugar than their fresh originals.

Prunes, dried dates, figs, apricots, peaches, apples and pears deliver energy when you are feeling tired and make great snacks … provided they have been dried in the traditional manner without being infused in a sweetener.

By removing most of the water, drying concentrates the fruit’s natural sugars whichever method is used. To obtain the same total sugar and energy, the amount of traditionally-dried fruit you eat should only be about 1/3 of the amount of fresh fruit you would eat; otherwise you’ll send you glucose level soaring.

You should of course avoid dried fruit that was infused with sugar before drying.

A bad cold or flu

Your blood sugar rises when your body is fighting an illness, especially if you are diabetic. Being diabetic makes it harder for you to handle infections such as influenza.

In addition, illness can prevent you from eating properly, which will also affect your blood glucose. Some medicines, such as antibiotics and the decongestants for your sinuses, can raise blood sugar.

Some medicines for colds contain sugar or alcohol. Although the sugar content is small, it is best to use sugar-free and alcohol-free products. You should ask your pharmacist about the possible effects of over-the-counter products before you buy them.

The solution for colds and flu is to avoid contact with people who have colds or flu as far as possible.

You should also have a flu shot once a year. A diabetic who gets a bad dose of flu is three times more likely to be hospitalized due to the flu and its complications compared to other people.


When you’re stressed, your blood sugar levels rise, especially if you have type 2 diabetes. This is due to stress hormones such as cortisol.

This is not surprising as the major functions of these hormones is to boost energy by raising blood sugar so that you have the energy you need to fight or flee.

These hormones can be increased by both physical and emotional stress.

You probably know what increases your level of stress and can judge roughly when it is low, medium or high. You can match your stress with you blood glucose levels by recording your stress level (subjective though this will be) whenever you check your blood glucose.

Once you begin recording your stress levels, you’ll be able to figure out what levels of stress make your blood sugar go up.

Once you know what stresses send your blood sugar levels soaring, you’ll need to devise ways to chill out.

Do whatever relaxes you. Learn to unwind with deep breathing and exercise. If possible, change the situation that is making you feel excessively stressed.

Steroids and diuretics

Drugs known as corticosteroids (steroids) are used to reduce inflammation in the treatment of asthma, arthritis, rashes and other conditions. However they can cause your blood sugar to rise, and may even trigger diabetes in some people.

To achieve their purpose, corticosteroids mimic the action of cortisol, a hormone that is released when you are under stress and which (as discussed above) increases your blood pressure and blood glucose levels so that you are ready to fight or flee.

High blood glucose levels whilst taking steroids may subside after you stop taking steroids. However, if you take oral corticosteroids for more than three months, these excessive levels may become more persistent and you are likely to develop type 2 diabetes.

Diuretics (water pills) are used to treat high blood pressure. They can also raise blood sugar levels if you have diabetes. Thus you should never take diuretics unless they are prescribed by your doctor who should be well aware that you have diabetes.

Author: Paul Kennedy

Paul D Kennedy is a qualified accountant and an international business consultant who used his skills as a researcher to uncover the mysteries of type 2 diabetes and gain control over his health and wellbeing.

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