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do carbs affect blood sugar
Table sugar made up of glucose and fructose.

Do Carbs Affect Blood Sugar?

The body receives fuel from 3 kinds of foods (building blocks): carbohydrates, fat, and protein. Carbohydrates (carbs) are plants such as vegetables, fruits, grain, milk, and sugar cane. Protein comes from animal products such as eggs, meat, fish, chicken, cheese, and dairy. Fats come from fatty vegetables such as avocados, olive oil, and nuts. Do carbs affect blood sugar? Definitely, but you need to understand how the digestive system functions.

The digestive system made up of the stomach and small intestines breaks down each of the building blocks before absorption into the blood stream. Hormones are molecules that deliver messages to a target cell. Insulin secreted by the pancreas delivers the message to most body cells to take glucose out of the blood to use for energy.

For message delivery, hormones must attach to the target cell by binding to receptors on the cell surface, much like a lock and key. Insulin acts on the insulin receptor to bring glucose into the cell. Insulin is the key and fits perfectly into the lock (the receptor). The door opens, and glucose enters.

Reference Dr. Jason Fung – The Obesity Code: Unlocking the Secrets of Weight Loss.

What is blood sugar?

Blood sugar is known as blood glucose or glucose. It is glucose that is broken down from refined carbs such as table sugar, bread, rice, potatoes, and pasta. The chemical formula of glucose is C6H12O6 and is a simple carb called a monosaccharide. Reference from http://www.biology-pages.info/C/Carbohydrates.html.

Sucrose is known as table sugar, composed of 2 monosaccharides bonded together from fructose and glucose. Fructose is the sweet part of sugar and goes straight to the liver and is stored as fat. In the US only sucrose can be called sugar. All of the other sweeteners which are carbs cannot be called sugar. Note that Sugar-Free on a package means that it is supposed to be a healthy or low-calorie substitute and they are replacing sucrose with another sugar related to it. They are all from the sugar family of sucrose.

Carbohydrates are chains of sugars, broken down into smaller monosaccharides. When the glucose enters the bloodstream, the body needs insulin to process the glucose. It will need very little for the amino acid and fatty acid, from animal products and fatty vegetables.  Dietary fiber is not broken down through digestion; it moves through the body without being absorbed and usually expelled as waste.

Body Cells

All cells in the body can use blood sugar (glucose). Certain foods, particularly refined carbohydrates, raise blood sugar more than other foods. The rise in blood sugar stimulates insulin release. At mealtimes, ingested carbohydrate leads to more glucose being available than needed. Insulin helps move this flood of glucose out of the bloodstream into storage for later use.

The body stores glucose by turning it into glycogen in the liver, this process is called glycogenesis. (Genesis means “the creation of,” so this term means the creation of glycogen.) Glucose molecules are connected together in long chains to form glycogen. Insulin is the main stimulus of glycogenesis. The body can convert glucose to glycogen and back again when needed.

But the liver has only limited storage space for glycogen. Excess carbohydrates become fat, this process is called de novo lipogenesis. (De novo means “from new.” Lipogenesis means “making new fat.” De novo lipogenesis means “to make new fat.”)

Glucose Test

There are methods to test glucose and can be performed by a 10-hour fasting, and then a blood sample is taken. Another test is the 2-hour, and 3 hour glucose tolerance test (GTT) – for this test, the person has a fasting glucose test done, then drinks a 75-gram glucose drink and is retested. This test measures the ability of the person’s body to process glucose.

Over time the blood glucose levels should decrease as insulin allows it to be taken up by cells and exit the blood stream. I am not a fan of this test as it causes the glucose to spike sharply. A type 2 diabetic does not need to take this test, it only confirms.

I use a Contour EZ Next glucometer with test strips, any carb can be tested this way. To verify that a carb does affect blood sugar. Set a baseline by checking glucose before ingestion of a carb, or protein, then take a  glucose reading 45 minutes after ingestion. Fats will not have any impact on glucose or insulin.

Watch your Carbs

If you want to eat carbs, then you will need to do some carb counting. Dr. Bernstein (the legendary diabetologist) recommends that the carb intake per day equal 42 grams or less.  If you follow this guideline, you should be golden. Take note; everyone is different and you will have to experiment on yourself.  Obviously if you eat a bag of potato chips you have defeated the purpose. By following a Low Carb High Fat (LCHF) Diet, or Ketogenic diet you should be good.

Now that you know which foods you should not eat and to keep the carb count down, I would suggest you eat the following foods:

Leafy vegetables, meat, chicken, fish, eggs, high fats, butter, olive oil, cheese, avocados, cauliflower, broccoli, coconut water, water, coffee, tea, onions, tomatoes, high-fat unsweetened yogurt, and nuts in small quantity. Fruits are OK in very limited quantities too.

Consult your doctor before making any dietary changes. Only you can help yourself, go to your doctor and get your Hemoglobin A1c test. Then get a glucometer to check yourself at home.

Please take action, try to follow the simple guidelines. Only you can help yourself. I am on your side, with a little bit of self discipline you can control your carb intake so as not to raise your blood sugar.

Finally, do carbs affect blood sugar? The answer is yes, carbs and protein affect blood sugar. A type 2 diabetic must severely limit the amount of sugar, added sugar, and processed foods. Keep your blood sugar low and your insulin resistance will normalize also.


I welcome and appreciate comments, question and concerns. Please send me an email.

Many thanks for dropping by and reading this post.

To your good health.


Carbohydrates  http://www.biology-pages.info/C/Carbohydrates.html.

Recommended Reading (See also Recommended Books To Read)

The Obesity Code: Unlocking the Secrets of Weight Loss, Jason Fung, Greystone books, 2016.




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10 thoughts on “Do Carbs Affect Blood Sugar?”

  1. Hi Jimmy, I like reading your post about diabetes and carbs. It is informative and scientific. I am a type 2 diabetic that is why I took note of the details. I check using the glucometer and test strips and I test twice a day. I do not observe the diet very strictly, I let the medicine take care of it. But I eat all the food you mentioned except that I eat only a few type of veggies. But I eat broccoli and cauliflower which you also mentioned. I find your post very helpful.

    1. Hello Rebecca,

      I appreciate that you found this post helpful and that you eat a few type of veggies, broccoli and cauliflower.

      What type of medication are you taking? 

      What is your A1c?

      There is no need to check your blood sugar level 2 times a day unless you are checking specific foods. For example eat something and measure your blood glucose.

      I would try to get off of the medication and to do that you need to reduce your carb intake. Carbs are the same as sugar so start by eliminating sugar. Next step is to start with a Low Carb High Fat (LCHF) diet then if you want to take it to the next level start on the Keto diet.

      The Keto diet is the extreme version of LCHF which limits your carb intake to 20 grams per day.

      The next step is to do some intermittent fasting, try to do it  2 times a week and you will be burning calories, losing weight and lowering your A1c to a point that you will want to maintain it like myself.

      Please read my other posts and if you need more information send me an email and I will help you as much as I can.

      Please double check with your doctor or health practitioner before making any changes to your lifestyle.

      Thanks for dropping by and commenting.


  2. Well, I’m neither pre or diabetic…but definitely curious. I get the part about the low carb…But how much fat should you eat? How much is considered high fat. I imagine that too much fat is not healthy either. If your body isn’t using it, the excess will be converted to stored fat? So what’s the limit on that in terms of grams?

    1. Hello Dave

      In response to your questions: 1. How much fat should you eat? The theory of the Low Carb High Fat (LCHF) diet is to eat when you are hungry and then until you are satisfied. Eat only natural foods and cut high processed refined carbs and sugar out of your diet. A quick example: for breakfast, I would eat a 2 egg omelet cooked in 1 TBSP (15 grams) of butter with a 1/2″ cube of cheese (60 grams, 40 % fat, and 240 calories). With a coffee and use 2 TBSP of whipping cream (30 grams, 33 % fat and 125 calories).

      2. How much is considered high fat? The high fats would be butter, whipping cream, cheese, avocados, and olive oil. These are all natural and healthy high fat foods. The unhealthy fat foods are trans fats otherwise known as partially hydrogenated oils which are used in fast food cooking, snacks and processed type foods.

      3. If your body isn’t using it, the excess will be converted to stored fat? It will be if it is not burned off. I lost 30 pounds using the LCHF diet and Intermittent fasting 2 times a week and have now managed my type 2 diabetes to the point that I do not worry about it. I can lose weight at will by fasting.

      4. So what’s the limit on that in terms of grams? I have never actually measured a limit in terms of grams, but if you eat meal by meal and not over eat by following the LCHF diet you should be good. Cook your meals in butter 1 or 2 TBSP or up to 30 grams, I usually eyeball a good tablespoon. You can cook meat, chicken or fish in the butter. Again I stress eat until you are satisfied. If you want a side salad use olive oil (2 TBSP or 30 grams) with a mixture of natural ingredient salad dressing.

      Thanks for reading the post and commenting.


  3. Carbs absolutely affect blood sugar. At least the simple carbs do. It’s the complex carbs that you want and are good for you. As a diabetic I have to know all about diabetes and blood sugar levels. You have to be very careful about what carbs and sugars you eat. The most important things are checking your blood sugar, eating right and exercising. So take the advice from the foods listed here and watch your carbohydrates. Nice article!

    1. Hello Rob,

      I appreciate the comments.

      As a diabetic you absolutely have to watch your carb intake and if possible eliminate sugar from your diet. Do a blood glucose check everyday eat right exercise and if possible start Intermittent Fasting. The Intermittent Fasting will burn calories and weigh in no time. If you are a type 2 diabetic you will drop your A1c to a safe level very fast.

      Thanks again for dropping by.


  4. Hey Jimmy

    I love yr post! It is very informative and interesting.:)

    I didn’t know our carbs intake per day should equal 42 grams or less, that is great information for me. I am now trying to cut down on carbs and fats and eating more vegetables..

    My mum is a diabetic and it is not easy on her as she has to control her craves on sugary drinks. I always ask her to eat more vegetables and fruits instead … Sometimes I do sympathize with her as I know she is trying her best on her food diet.

    Thanks for yr awesome post on “Do carbs affect blood sugar”, keep up yr great work. 🙂

    1. Hello Jewel
      If you are not diabetic the 42 grams per day is not a must thing to do, but if you are diabetic you need to lower your carb intake. Anybody should lower and cut down on the sugar intake natural or be it sweeteners.
      Please inform your mum and have her drop by the site for any more information.
      Thanks for reading the post.

  5. Your diagrams brought me right back to my days in Biochemistry class. I am glad those days are over.

    You mentioned the 2 hour glucose tolerance test. What’s even worse is the 3 hour GTT where a fasting sample is taken, 75g of glucose given, then samples are taken 1 hour, 2 hour and 3 hours after the ingestion of the glucose. Not pleasant at all.

    Paying attention to your diet as you suggest (and I will add, leaning towards a plant based diet) is a good step towards controlling your blood sugar levels.

    Thanks for the reminders.

    1. Hello Freddie

      Thanks for your comment. Are you a type 1 diabetic? I believe in the LCHF diet, it is working for me.

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