Are you confused about whether your diet is healthy?

Are whole grains good for us?

Do we need to be gluten-free?

Should we be eating dairy regularly?

What about fruit?



With all the conflicting diet information out there, it’s enough to drive you crazy trying to figure out the right approach! Where do you even start?

Fortunately, it actually doesn’t have to be complicated.

The impact particular foods have on your health can be quickly identified by one very basic measurement: your blood sugar. 

Having a normal functioning blood sugar is the key to optimal health and the prevention of chronic disease in your life. Virtually all chronic diseases are either caused by poor blood sugar control or are improved by better blood sugar management.

But first, let’s look at the very basics.

What Is Blood Sugar? 

Blood sugar, or glucose, is the sugar found in your blood that comes mainly from the food you eat. Whenever you eat something, your digestive system breaks it down into smaller components, and one of the major components is glucose. 

Glucose is our bodies’ preferred energy source. It’s a necessary ingredient for maintaining the optimal function of your organs, muscles, and nervous system.

If you just ate a meal high in carbohydrates, starch, and/or sugar, your blood sugar will rise high over a normal fasting level. If you just had a meal of healthy fats and proteins, your blood sugar will not rise as high.

Blood sugar after meals that is continuously outside of the normal range can lead to major blood vessel and body tissue damage.

This damage creates toxic compounds called advanced glycation end products (AGEs). 

AGEs are proteins or lipids that are tagged with glucose molecules as a result of continuous exposure to high sugar levels. AGEs accelerate the aging process by depleting your body’s antioxidant stores. 

They also wreak havoc in the body by damaging DNA and lead to the development, or worsening, of many diseases including diabetes, atherosclerosis, high blood pressure, kidney disease, and Alzheimer’s disease. 

Fortunately, it’s very simple to measure the direct effect on your blood sugar of any kind of food, whether it’s a bowl of greens or a big juicy burger. 

That means you can always make an informed decision about your dietary choices and ensure that you have the data you really need to optimize your health over the long term.

How To Test Your Blood Sugar

To test your blood sugar at home, all you need is a very inexpensive piece of equipment you can find at any drug store or pharmacy called a glucose meter or glucometer.

Glucose testing from home using a glucometer is typically done by a finger stick test. This involves pricking the tip of your finger and collecting a small drop of blood onto the testing strip.

Here is a glucometer that I recommend, which includes 100 testing strips and 100 lancets. 

Click here for a video tutorial on how to test your blood sugar.

The test itself is very mildly painful but if you are feeling squeamish, I recommend having someone else help you with the finger stick because it may be harder to do on yourself.

Here are the data points that you will want to track when assessing your body’s response to meals: :

  • fasting blood sugar levels
  • blood sugar 1 hour after eating
  • blood sugar 2 hours after eating
  • blood sugar 3 hours after eating
  • how long it takes for blood sugar to return to fasting levels after eating 
  • a diary of foods eaten before the tests

Let’s work through the best way to test your blood sugar and get all these data points.

First: Test your blood sugar first thing in the morning before you have eaten anything.

This is called your “fasting” blood sugar level. Optimally this level should be between 82-88 mg/dL (4.55-4.88 mmol/L). Conventional medicine considers anything <100 mg/dL (5.55 mmol/L) as normal. 

Second: Test your 1-hour post-meal blood sugar. 

Your blood sugar will reach its highest point around 1-hour after eating the meal. This reading tells you how high your meal has made your blood sugar. It is important that you are not eating food that consistently raises your blood sugar over 120 mg/dL (6.66 mmol/L).

Third: Test your 2-hour post-meal blood sugar. 

This reading tells you how efficient your body is at balancing your blood sugar. Optimally this level should be less than 120 mg/dL (6.66 mmol/L). The closer to 100, the better. 

Fourth: Test your 3-hour post-meal blood sugar.

Your glucose level should be back to your fasting level or under 100 mg/dL (5.55 mmol/L). This is a normal healthy response to eating a meal.

Fifth: If your blood sugar has not returned to your fasting level by hour three, continue to test it hourly until you see how long this process takes for your body. A normal response is 3 hours post-meal.

In the beginning, it is a good idea to pick some meals that you eat on a regular basis and take a day to test those. 

Record your findings. And as time goes on, you will have a diary of what foods your body responds to best.

Ready to get to work on improving your own blood sugar levels? Interested in working with a doctor to finally nail down the best diet for your body and health? Click here to complete a short application to start working with Dr. Alexis Shields.  

Normal vs optimal blood sugar ranges

I’ve written extensively about the difference between normal and optimal blood markers here, and the same applies to your blood sugar ranges. 

From the perspective of conventional medicine, a fasting blood sugar level of 100-125 mg/dL (5.6-6.9 mmol/L) indicates prediabetes.

Two consecutive fasting glucose levels of ≥ 126 mg/dL (7.0 mmol/L) indicates diabetes, as well as a random glucose reading of ≥ 200 mg/dL (11.1 mmol/L), and a 2-hour post-meal reading of ≥ 200 mg/dL (11.1 mmol/L).

But much of the data in conventional medicine comes from populations who are not enjoying optimal health.

So what does a healthy daily glucose response look like from the perspective of preventative medicine?

On waking: Research indicates that your optimal glucose after waking in the morning should be between 82-88 mg/dL (4.55-4.88 mmol/L). This level is associated with optimal aging, the lowest risk of chronic disease, and the lowest mortality risk.

(Of course, there are always exceptions. Some people experience something called the “dawn phenomenon” in the morning and their fasting glucose level is slightly elevated above 88 mg/dL. This can be a normal response to cortisol raising in the morning. If this occurs, avoid eating for an hour and then observe your 1-hour post waking glucose level.)

After meals: Blood sugar peaks between 1 and 2 hours after the meal and should be back down to fasting levels by 3 hours post-meal. From the perspective of optimal health, you should avoid regularly eating foods that raise your blood sugar over 100 mg/dl (5.55 mg/dL).

One strategy to test the impact of your diet on your long-term health is to measure your blood sugar before and after meals. 

How to Improve Blood Test Results

Identifying the foods or meals that regularly spike your blood sugar too high, too fast, or too long can help you to individualize your diet for longevity.

After a few weeks of testing your blood sugar levels after eating various types of food, you should have a clear record of how your body responds. 

By familiarizing yourself with the effect that food has on your blood sugar, you will start to learn what foods your body loves and which ones to eat only on special occasions or not at all. 

A balanced blood sugar results in a greater sense of wellbeing, having more energy, preventing the afternoon crash and feeling “hangry” (hungry + angry), and getting a better night’s rest. 

Here’s what It feels like to have normal blood sugar:

  • No extreme hunger between meals
  • No sleepiness after meals or mid-day
  • Balanced mood
  • Stable energy
  • Restful and refreshing sleep
  • Mentally sharp

Symptoms of High Blood Sugar (in a non-diabetic person):

  • Feeling fatigued and sleepy, especially after meals
  • Poor brain function and focus
  • Increased thirst
  • Frequent urination
  • Dry mouth
  • Weight fluctuations

But what does it mean if you eat something clearly unhealthy, like a candy bar or burger, and your blood sugar does not elevate over the 120 mg/dL (6.66 mmol/L) mark? 

This means your body is adapting to the rise in blood sugar very well!

This is a good thing. You have a very healthy body. However, if you continue to eat processed foods high in starch and sugars, over time your body will slowly lose this ability to adapt. This is not a good practice. 

Want to know some foods that commonly convert quickly to sugar and cause a rapid high spike in blood sugar?

  • White foods: white rice, white potato, all forms of sugar
  • Refined grains: bread, pasta, crackers, baked goods, cereals, chips
  • Candy and sweets
  • Soda, juice, sweetened drinks

Consumption of processed sugar increases your risk for many chronic diseases including obesity, cardiovascular disease, diabetes, and non-alcoholic fatty liver disease (NAFLD).

If your blood sugar is too high, or if you’re simply experiencing some of the symptoms of high blood sugar after eating, the best thing you can do is to exercise. Exercise clears sugar from the blood so that it can be used as a fuel source for your muscles.

Different types of exercise work to a different extent for different people. To determine your individual effect from exercise, test your glucose levels before and immediately after different types of exercise. Going for a walk after meals or a quick high-intensity interval training (HIIT) session is a good place to start.

If your test results are consistently outside the healthy range, here’s what you do:

  • Test and record your levels
  • Get a blood test to further investigate other blood sugar related biomarkers: hemoglobin A1c, fasting insulin, triglycerides
  • Experiment with reducing foods high in carbohydrates and starches, especially low-fiber processed foods (ie. white bread) and those with added sugar (ie. salad dressings with sugar as an added ingredient, check your labels!)

Need a blood test to check your blood sugar related biomarkers? Click here, if you are in the US, to order your own blood test. 

And if you want help with these steps, click here to explore a Mini Health Review. After a simple blood test, I’ll review your data and come back to you with an action plan tailored to your specific needs. 

Symptoms of Low Blood Sugar (in a non-diabetic person)

  • Hunger
  • Feeling shaky or trembling
  • Mood changes — irritable or moody (“hangry”), anxious
  • Sweating
  • Tired
  • Heart rate fast or pounding
  • Dizziness
  • Sleepiness
  • Weight fluctuations

If your blood sugar is too low, the best thing to do is to eat a balanced meal based on the data you’ve collected since you started tracking your blood sugar after eating. 

If you don’t have enough data (or any) just yet, start with something that’s moderate in carbohydrate and also contains some protein and healthy fats. An apple with some nut butter is a good option, as is meat or seafood with some vegetables cooked in olive oil. 

Clearly, there’s a huge range in the effects different types of food have on your blood sugar.

That’s why tracking your blood sugar 1 hour after eating and your blood sugar 3 hours after eating over a few weeks can be such a valuable tool. 

When you’re learning how to improve your blood test results and optimize your long term health and longevity, you must have data as the foundation.

Your blood sugar is one of the fundamental indicators of your current and future health, and if you focus on this one metric alone, all the other biomarkers in your annual labs are likely to improve as well. 

Ready to get to work on improving your own blood sugar levels? Interested with working with an online functional medicine doctor? The Mini Health Review as an easy first step to getting started: click here to learn more.

    29 replies to "Want to know if your diet is healthy? Track your blood sugar."

    • Mary M. Martinez

      Thanks, very informative.

    • Sagar

      Hey thanks for the info.. btw I’ve some issues regarding my health, hope you would like to hear and love to comment on that! I’m an Indian and my family is having diabetes. My grandfather died in 1975 by kidney failure and my father has also diabetes but in control. I’m 33 years old and recently I’ve been diagnosed with diabetes.. My fasting was 169 and PP was 292 (:O) . Then I started to do Yoga and diet.. after one month my fasting sugar level was 110 and PP was 127. But today I accidentally checked my blood sugar just after two hours of the wheat porridge+milk+honey+banana meal as breakfast and the result was 115. Seemed fine but I checked my sugar level again after the lunch (after two hours) but this time I got 145. So, should I worry or not?

      • AH

        I talked to my doctor when I was diagnosed, and she said that a blood sugar monitor can kind of bee like a bathroom scale, it fluctuates frequently and can make the user feel a little “crazy” when they think they’re being good with diet & exercise. From my understanding (speaking to a nutritionist) bananas are very high in sugar- did you use the whole thing? Maybe try switching to 1/2 banana & see if that helps?

      • girt

        Honey is sugar too

      • Purplesky

        Post meal numbers will ultimately be between you and your doctor but between 150-180 is usually ok. I don’t have much luck with things like bananas, oranges ect. I guess bc of the sugar.

        • Ozoagu Philip Obiora

          Interesting and helpful. Very greatful

    • Alice

      Thank you for this information. When you say a breakfast of cereal.And.English muffins, please be more specific? Does it be unsweetened cereal,such as oatmeal with diced apple and raisins? Or can it be Cheerios?

      What would you put on the English muffins, jelly,.all-fruit spread,.butter,or.can I have one Half-Life in with butter, and the other half with jelly or all-fruit, please? Diabetic,and my morning fasting sugars have progressed this last year from an avg of95-105, to 95-120s, but the last 2 were 170 and 152.

      I’m not on medication..

      I only eat whole grains. I have a terrible time eating at the same times or every 3 hours,very chaotic to a starve-binge eating disorder that started by dieting and dieting exacerbates it, Spielberg diet again. I have starved/dieted/binged up to.370lbs, so dieting is the worst for me. I went for 30 years almost never eating before 4 pm,and it has taken half a.dozen years of eating disorder treatments to be able to eat breakfast most days. It’s 3 pm and I haven’t eaten breakfast yet. About to test and go eat.

      Also,why,.When I eats cup of ice.cream and other sweets at night or the previous day,is my blood sugar under 100.the next morning, but if I don’t eat sweets, the BG is over 100 – 120 the next morning, please? Thank you in advanced any help you might provide.

    • Alice

      I apologize for all the auto-word errors!


      Thank you for this information. When you say a breakfast of cereal and.English muffins, please be more specific? Does it be unsweetened cereal,such as oatmeal with diced apple and raisins? Or can it be Cheerios?

      What would you put on the English muffins, jelly, all-fruit spread, butter,or can I have one half with butter, and the other half with jelly or all-fruit, please? I’m Diabetic,and my morning fasting sugars have progressed this last year from an avg of 95-105, to 95-120s, but the last 2 mornings my readings were 170 and 152.

      I’m not on medication..

      I only eat whole grains. Other than sweets, I eat a home-made, mostly whole foods diet.

      I have a terrible time eating at the same times or every 3 hours,very chaotic due to a starve-binge eating disorder that started by dieting, and dieting exacerbates it. I will never diet again. I have starved/dieted/binged up to 370lbs, so dieting is the worst for me. I went for 30 years almost never eating before 4 pm,and it has taken half a.dozen years of eating disorder treatments to be able to eat breakfast at all, most days. It’s 3 pm and I haven’t eaten breakfast yet. So please don’t advise weight loss. It just triggers me to not eat, especiallybreakfast,and dieting and meal skipping restricting is a set-up for binging/make-up eating. I’m about to test and go eat now.

      Also,why, when I eat a cup of ice.cream and other sweets at night or the previous day,is my blood sugar under 100.the next morning, but if I don’t eat sweets, the BG is over 100 – 120 the next morning, please? This is driving me crazy. I read from Dr. McDougall that carbohydrates -probably he ONLY meant starches- stimulate the pancreas and help to maintain healthy BG, and I do have an intentionally whole-starch centered diet, but these blood sugar tests in relation to eating sweets are very confusing, and tempt me to eat sweets to get lower morning readings. I only test in the morning currently.

      Thank you in advanced any help you might provide.

    • Iluebe T.

      Thanks for these awesome post on blood sugar levels, very informative. Like your blog

    • Carol

      Hi, I have been told I am pre diabetic and decided to check my blood sugars at different times to see the trends. I’ve only been doing it for about a week but what does it mean if my fasting are consistently 100-06 but my post parandials are 135 or less (mostly 120 or less) . I’ve checked my glucose before bed and it was 88 but then 105 in the morning. The post parandials
      don’t seem bad but my castings are almost all in the prediabetic range.

      • Chris

        Honestly doesn’t seem too awful. I’m a healthy non diabetic 20 year old and while my fasting is in the 80s my post prandials are much higher than yours, often peaking at like 170 and then around 140 at 2 hours. I think everyone’s body is a little different. The amount of anxiety checking the blood sugar caused is certainly bad for me too! The suggestion to never go above 100 to be healthy is a little excessive. Most research indicates that even healthy people can spike well over 140 due to certain foods.

      • Ozoagu Philip Obiora

        Highly informative.

    • Health obsessed

      Thanks so much for the information. I am very interested in your work. I am 43 and had a Hemoglobin A1C 2 years ago that was 5.7. I changed my diet and got rid of all processed foods. A year and a half later, my Hemoglobin A1C was 5.5. Most recently, I became interested in what exactly is increasing my glucose values so that I can modify further. I ordered and placed a continuous glucose monitor (freestyle libre CGM). Using that, my fasting glucose is around 70 and after meals, I generally go up to around 89. Occasionally I may go as high as 104 if I eat fruit or a “healthy” carb. I am confused about what to believe…the hemoglobin A1C? Or the CGM? and Is going from 71 to 90 after a meal normal? Or should there be less of a gap? Is there a guide for how much you should go up after a meal?
      Thank you!

      • Kassi

        How do you get an order for a libre GCM. I live in the states and they are regulated. I can get stick and a meter. But for long term testing like weeks it can be hard on the fingers.

        • Kassi

          Thank you, I did find January and im doing a month with them. But my concern is I have been low carb eating less and 75 carbs a day for over a year and wonder if what they have me eating like doing a blood glocuse test on day 3 will give faulse results or to high of blood sugar, seeings I only consume about 23 grams of sugar or less a day. I bring this up because I got a meter and have been doing finger stick and notice heavy carb meals like 5o grams or more cause sugar spikes that would be concerning. but fasting glocose has ranged from 80-90 depending on what time i get out of bed and post meal lower carbs less than 40 grams carbs keep me within the optional range you list. I will follow up with levelshealth after I finish may January program that starts next weekend. Thank you for sharing your time and knowledge all times of the day, even when its incovient for you

        • Dr. Alexis Shields
    • karan joshi

      Hey, I Read Your Article, And Your Information Is Very Amazing And So Much Helpful For Me. Keep It Up And Thank You Very Much.:)

    • Jack

      Everyone should know type ll diabetes is almost 100% preventable and nearly always reversible by going on a low carb, moderate protein diet.

      • Melanie

        Agreed. Someone on a diabetes site said that the food pyramid they teach us is upside down and I agree. Many national diabetes sites promote eating things like oatmeal and whole wheat toast, as well as eating constantly, I believe they say so in order to balance out MEDICATION – insulin or metformin etc. so you don’t accidentally hypo. They say it’s a “progressive” disease. It’s like they use the same strategy as Type 1 which is not preventable or reversible and not the same. Low carb and intermittent fasting CAN reverse Type 2 diabetes, low carb prior can prevent it in many people.

        Thank you Dr for the info you have provided! A great step toward prevention.

    • Mycalcu

      Thanks for sharing information. Blood Sugar is very important for health.

    • Emma Smit

      I was dignoised with preiabetc, but was given Bigsens tablets to take, my morning fasting home test reads 5.1, one hour after breakfast it reads 8.5, can i have a explanation if I am reading correctly please Emma Smth

    • Elizabeth Raass

      My dr. Told me I’m boarderline diabetic. I have a family history of it. And I had gestational diabetes while pregnant, baby boy is healthy and 5 months now.

      I thought I could go back to eating whatever I wanted but in moderation. I was wrong. I have tried cutting back my carbs. But feel completely overwhelmed. My glucose was 142 after 2 hours after a meal filled with veggies a little beef and half a sweet potato and my mornings have been 99 to 113.

      I’m terrified of getting diabetes. Is there any healthy recipes for breakfast lunch and dinner you could share to help keep my glucose under control?

      Thank you so much!!!

    • Summer

      This is awesome. When a I am compliant with my eating plan, I strive to keep my post meal glucose levels under 100. I thought I was being insane. This is the 1st doctor to say I am spot on. I found a little trick to help as well. I never get near 120 but sometimes it inches up a little more than I would like. I hit the rowing machine for 10 minutes and it knocks it back down. I tried walking but it doesn’t bring it down fast enough for me. My BG goes down and I don’t get hungry afterwards either. Oh yeah, and my excess weight just flies off.

      I use a CGM. Insurance doesn’t cover it but my doc wrote me a prescription for it anyways. It is life saver and really helps me make informed decisions about what I put into my body. I cant wait until the smart phones finally release the cgm feature. That will be a game changer for health.

    • Amaya

      Gratitude for these amazing post on glucose levels, extremely educational. Like your blog

    • Shobhit Kumar

      As a diabetic, I highly recommend this innovative product. It’s user-friendly, accurate, and has made diabetes management much more manageable. click here to make a positive change in your diabetic journey!

    • Steve

      I am a type 2 diabetic using Metformin. Occasionally when on a trip or vacation I will eat food I don’t usually eat & drink. I monitor my levels with a Dexcom 6 and they may get up to 200. Once I return home and go back to my diabetic type diet it seems to take 3-4 days for my levels to stabilize back to my norm of 110-120 resting. Why does it seem to take that long to get back to my lower numbers?

    • William Thomas

      That is amazing. Thank You For This Information.

    • Rajkumar Ghosh

      This is pretty useful information. Thank you for sharing this.

    • Red

      thank you, this is exactly the information I need to understand the mystery of diabetes. I have been serious about what I eat since my doctor told me I was pre-diabetic. my FBS is now down to below 90 with the occasional above and I have been sleeping better.

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