Last week we looked at why it is important to measure how our body responds to different foods regarding blood sugar spikes. This week we will look at how we measure this, and what our optimal goals are. It’s time to do your own experimentation.

From last week’s post, we saw that we each respond differently to the foods that we eat, in terms of how much a blood glucose spike they cause for us; that is, our post-prandial glucose response (PPGR). For some people, eating a banana will cause a large PPGR, but for others, there will be little response.  

To date, we’ve frequently been told to look at “glycemic index” or “glycemic load” to predict our glucose response to food. However, those values are for single food items only and don’t reflect meals, which are combinations of ingredients. From the personalized nutrition study I spoke about last week, it now seems that our glucose response to a meal is influenced by not only the food itself but also our genes and lifestyle, including blood parameters, previous dietary habits, anthropometrics (body size measurements), physical activity, and our gut microbiota. Yes, even the bacteria that live in our gut play a role in our response. 

While the authors of this research are busy trying to set up a company to help people tailor their ideal meals so as to avoid after-meal glucose levels that are too high, we can go a long way towards this ourselves with some simple monitoring.

Measuring your post-prandial (after meal) glucose response (PPGR)

The approach I take to see how an individual responds to different foods is to use a glucometer to test blood glucose levels before a meal, one hour after a meal, and then two hours after a meal.

A glucometer? It sounds big, but in reality it is a very small device that is very easy to use. It needs just a single drop of blood, easily obtained by a quick finger prick (so small that you’ll barely feel it). The equipment is readily available at your local store but is often less expensive on Amazon. Here are links to reasonably priced kits that contain all you need:
GlucometerThis kit includes glucometer, lancets and lancet device (the finger prick needles and the device they fit into), paper test strips, log book for results and a carrying case: HealthPro Glucose test kit from for $14 and here’s a similar one from called Exactive Easy for £15. Other kits are available too, so you can shop around. Be sure to check the price of the test strips as some brands are expensive.

To use the kit, you put a lancet in the lancet device and a paper strip in the glucometer. Then wash your hands in warm water and dry them well.  This will also help warm your fingers so it’ll be easy to get the tiny drop of blood. Then prick your finger on the side of finger tip (less sensitive area) with the lancet, and touch the tiny drop of blood onto the paper strip. The meter then tells you your blood glucose level. Quick and simple.

When to measure your PPGR

For the moment, there are two types of blood glucose level that we’re interested in: your fasting blood glucose level (when you haven’t eaten for a few hours), and your PPGR level (taken immediately before and then shortly after eating). The test procedure is the same in both cases.

  1. To measure your fasting blood glucose level, test your blood sugar first thing in the morning, before eating. Try to get into the habit of doing this every day, for as long as it takes to see a pattern. 
  2. To measure your PPGR, test your blood sugar before a meal, then measure it again one hour after eating, and then two hours after eating. You can often skip the pre-meal test if it’s around the same time as the fasting test, or if you’ve only recently tested your level.
  3. Write down your results in the log book that comes with the meter or enter them into the Health app on your phone. The iPhone Health App that comes with the phone is all set to record blood glucose levels.

Don’t be put off by the idea of pricking your finger. You can do it. It doesn’t hurt. And it’s easy, so you’ll get into the swing of doing it. 

Now we are ready to look at how your PPGR relates to the meals you eat. 

What are you looking for?

Here are some goal numbers, utilizing all three measurements – fasting blood glucose from first thing in the morning, 1- and 2-hour post meal glucose, and your hemoglobin A1c (HbA1c) measurements from your doctor.

USA levels, measured in mg/dL

Table of optimal blood glucose levels after eating a meal from

UK levels, measured in mmol/L

Table showing recommended blood glucose levels using UK units, from blog

These numbers come from studies where glucose is continually monitored. The American Diabetes Association (ADA) uses the average population to get their levels; however, with rising blood glucose levels globally and rising incidence of pre-diabetes and diabetes, the ADA normal levels might not be the best goal to aim for. If you want optimal health and longevity, we can do better than average, so aim for the optimal levels.

(For simplicity in the rest of the post, I’ll refer only to the US values (otherwise it gets confusing because of the different units used to measure glucose in the UK and US).)

If your fasting blood glucose levels are regularly higher than 99mg/dL (shown as “99” on your glucometer), you should talk to your physician about being thoroughly tested for metabolic syndrome and diabetes. And see a registered nutritional therapist. Healthy fasting levels are typically between 70-85 mg/dL. However, people on very low carb diets might have higher than normal blood glucose levels, making their post meal and HbA1c levels even more important to monitor.

Three other situations where I recommend you see your physician are when:

1) Your blood glucose is consistently below 70 mg/dL, as this could indicate hypoglycemia.  

2) Your PPGRs are consistently high 1-hour after eating (>180mg/dL).

3) You are concerned about your results for any reason.

The goal is that your blood sugar doesn’t CONSISTENTLY rise higher than 140 mg/dL one hour after a meal or 120 mg/dL two hours after a meal. Some variation is expected but if your levels are consistently above the targets, you might want to look at your carbohydrate intake and make adjustments.

Your own experiment

So now that we know how to measure our levels and our goals, the fun begins!  You can get going and experiment on yourself! This is a large study of n=1 — with you as the only participant!

While it might seem like a lot of finger pricking to start with, most of us eat quite repetitive meals so you won’t need to test all the time. For example, eat your standard breakfast and do the 1- and 2-hour post meal tests. If you see a large spike in your level from your pre-meal test – that doesn’t resolve in a couple of hours – try making some changes to your breakfast the next day. For example, you can switch fruits, or use less of something, or add some fiber, such as flaxseed, and retest the new breakfast. If it’s something you eat regularly, such as your standard breakfast, it’s good to tweak it until you find something you enjoy but that doesn’t spike your levels.

Make sure you keep good records of both your numbers and what you’ve eaten. You’ll soon figure out which foods  cause the spikes and which foods lead to a relatively flat glucose response.  

Changes you can make

If you find certain meals cause a spike in your levels, there are several things you can do:

  • Reduce the amount of the carbohydrate in that meal.
  • Switch one food in the meal for another that might cause less effect. For example, instead of rolled oats try steel cut oats.
  • Cinnamon helps regulate blood glucose levels, so consider adding 1/2 teaspoon of cinnamon to your diet daily. Make this part of your experiment and see if it works for you.
  • Add some more protein or fiber/resistant starch to the meal.
  • Include fermented foods with the meal, like fermented vegetables.
  • Make sure you are adequately hydrated. If you are under hydrated, your blood sugar levels will be higher. 
  • Exercise helps lower blood glucose levels too, as the glucose goes into the muscle for energy. So if you have a high carbohydrate meal, consider exercising or going for a walk afterwards.

Another thing that you might find affects your levels is stress. So bear this in mind if you find your results much higher on a stressful day. It might not be the food but rather the stress that is causing those elevations.  Don’t just ignore this however – this should motivate you to do some stress reduction!

And yes, these relatively inexpensive meters are not 100% accurate (what test is?) but we are looking for patterns, and they are definitely accurate enough for that. 

The goal is not to have raised blood glucose levels that stay raised over a long period of time. If levels remain raised, this can cause inflammation, damage to insulin producing cells, damage to nerves, and increased risk of diseases like stroke, Alzheimer’s disease, cardiovascular disease, and cancer. You definitely want your levels to be decreasing back to (if not already at) their original level by the 2 hour time point.

My own experience

Last winter I was eating quinoa with berries and homemade soy yoghurt for breakfast. I loved it; it was warming. But when I tested my levels, I found it created a big spike in my blood glucose levels. The quinoa was providing good protein, fiber, and micronutrients, but it wasn’t suiting ME. As this was a meal I had daily and it was causing high blood glucose levels, I decided to change it. I switched out the quinoa and just had ground flaxseed instead with the berries and yoghurt. The result? No impact on my blood glucose, it tastes yummy, and so that is my go-to breakfast now. 

Another food spike for me is bananas. They shoot my levels up above 140mg/dL. However, I have found that if I exercise after eating a banana, it reduces the spike. So now, I eat bananas before I do a workout or go on a strenuous hike. That way, the exercise pumps the glucose into my muscles rather than keeping it in the blood.

Now I’ve made adjustments to my diet through my own monitoring and experimenting, my levels typically start with a fasting blood glucose in the high 70’s or low 80’s; one-hour post meal rarely goes above 100mg/dL, and it’s normally back down to the 80’s within two hours. And I feel great.  

I don’t monitor all the time now. But I always check my fasting glucose level in the mornings. Then if I’m eating something unusual, I might just take some readings out of curiosity!

Now it’s your turn!

If you have any queries about your levels, feel free to get in touch and don’t hesitate to talk to your physician if you are concerned. In fact, it’s a great idea to tell your physician that you are doing this and share your results with them.

Give it a try. You’ll be fascinated. The glucometer can be one of our most powerful tools for preventing disease and living optimally. And who knows what YOUR perfect food may turn out to be? You might be surprised.

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