Evidence-Based Nutrition For Chronic Disease Prevention

Blood Sugar Spikes, Reactive Hypoglycemia, and How to Avoid Them: An Interview With Dr. Penny Figure

Published on May 24, 2023

In this video, I am having a conversation with Dr. Penelope ‘Penny’ Figtree, a primar care physician from Port Macquarie on the East Coast of Australia. In her office, she is focussed heavily on using dietary approaches, particularly low-carb diets, to treat obesity, type 2 diabetes, and other metabolic diseases. She also has some unexpected personal experiences with blood sugar spikes, frequently also followed by episodes of reactive hypoglycemia.

In this video, we are discussing the value of continuous glucose monitors to identify which foods lead to blood sugar spikes and reactive hypoglycemia, how such spikes and the following low blood sugar levels can be avoided, and how regular spikes to just one food can even lead to a diagnosis of pre-diabetes if eats eaten regularly.

Connect with Dr. Penny Figtree

Low-Carb Port Macquarie. Dr. Figtree’s office: https://www.lowcarbpmq.com.au

On Facebook: https://www.facebook.com/groups/829022994702336 

Twitter: https://twitter.com/PenelopeFigtree


  1. Wyatt et al.; Postprandial glycemic dips predict appetite and energy intake in healthy individuals. Nature Metabolism 2021; 3: 523-9.
  2. Norwitz et al.; Metabolic health immersion for medical education: a pilot program with continuous glucose monitors in medical and dental students. American Journal of Lifestyle Medicine 2022; ePub ahead of print August 15.
  3. Ludwig et al.; High glycemic index foods, overeating, and obesity. Pediatrics 1999; 103: e26.
  4. Summary of research on normal postprandial blood sugar levels vs. blood sugar spikes, and the impact of blood sugar spikes on chronic disease risks: blog post Blood Sugar Spikes – Q&A  from May 10, 2023.

4 Responses

  1. Critical question- I’m not diabetic nor am I pre-diabetic. But…

    Was it the smoothie in general that spiked blood glucose or was it the ensure product in the smoothie?

    I have a smoothie every morning for last 8 years. I don’t use any kind of powders, just ½ medium banana, ¼ blueberries, greek yogurt with fat, ¼ pear, oz or peanuts or freshly ground peanuts… those kind of ingredients. About 16oz typically but was thinking to reduce to 10oz.

    1. My best guess is that it was the combination of lots of fruit in liquified form plus the starch and sugar from the protein drink. In general, I think people with glucose intolerance should be very careful with ‘liquid’ carbs. If you have this regularly, you may want to check a few times what your blood sugar does when you drink it. You can do this with a hand-held glucose meter as well, as long as you measure a few time points within the first 60-90 minutes after taking the first sip.

  2. I’ve lived with Reactive Hypoglycemia for the longest time. And I’m so familiar with the shakes and fainting and fuzzy-headedness that Dr. Figtree is talking about!

    The way I identified it many years ago was through a Kraft Assay – which is a type of extended OGTT coupled with Insulin tests along the way. In India, when my lab runs an OGTT, blood sugar is tested at fasting, followed by a glucose load, and then blood sugar is tested every 30 minutes for either 2 hours or 4 hours, depending on the ask. When I added in the insulin test at each of those tests, I caught the massive insulin spike that leads to the Reactive Hypoglycemia I experience upon eating simple/naked carbohydrates.

    Although Joseph Kraft never discussed this type of hyper insulin response, I find that it’s common. I’ve been wondering whether it’s a genetically wired hyper insulin response to carbohydrates or then caused by a learned response to insulin resistance. My HbA1c is 4.4%. Obviously because of the lows coupled with the low-carb approach I follow to prevent the lows! And to think I’m possibly headed towards more carbohydrate intolerance due my way of eating!

    1. Hi Madhavi,

      Thank you for sharing. It’s important to be clear that the Kraft test is not per se just a test of insulin resistance. For example, if someone has a lacking first-phase insulin response (check out my answer to question #6 in this video here https://youtu.be/LVw60RIhbzg if you haven’t seen it), then blood sugar would be expected to rise a lot immediately after eating, particularly after eating ‘naked’ carbs (as in an OGTT). That huge rise in blood sugar would then stimulate a more substantial second-phase insulin response, which may seem like insulin resistance, but that’s not necessarily the case. One would need to consider the rate of glucose disappearance in relation to the ambient insulin level, and if someone develops hypoglycemia in that second phase after a meal I’d say glucose disposal would have to be very good, and that would be indicative of very good insulin sensitivity.

      A diminished first-phase insulin response is one of the earliest indicators of an increased risk of type 2 diabetes, and – by the way – is mostly genetically determined. Particularly among Asians, a genetic propensity to a diminished first-phase insulin response is often the key problem. See this paper here:


      Now note that being on a low-carb diet can also (temporarily) lead to a diminished first-phase insulin response. Because the first-phase insulin response is from pre-formed insulin, and why would the body keep insulin pre-formed in the beta-cells if never any carbs are eaten? So yes, being on a low-carb diet does make you more glucose intolerant due to a diminished first-phase insulin response, but by all accounts, this seems to be a temporary issue that can be reversed by eating carbs again.


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