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Things That Spike (and Crash) Your Blood Sugar

Blood sugar spikes are harmful to your health, and low dips can be as well—but they can be avoided. Learn more + how to manage your blood sugar.

Blood sugar spikes are something you want to avoid. Each spike can have long-lasting effects on gene expression in mammals.[1] And metabolic diseases like diabetes and heart disease—not to mention obesity —are caused by a lifetime of glucose spikes left unchecked.

For the record:

  • a spike is when your glucose jumps 30 mg/dl or higher
  • you can’t really avoid all spikes while remaining human. We recommend keeping daily spikes to two or less

So…what are the worst offenders that you should know about? And how can you help prevent glucose spikes in the future? Read on to find out.

Things that can SPIKE your glucose:

1. Food

You’ll notice that carbs affect your glucose more than protein or fat, and that some carbs spike you more than others.

Processed foods (chips, soda, anything packaged) will have less fiber and will spike you much more than a piece of fruit or a veggie/grain dish.

The game is to see which foods don’t cause spikes, and to stick with those foods for the most part. (And since everyone is different, a CGM that measures YOUR individual glucose response can help.)  

2. Exercise‍

Hard workouts trigger stress hormones like cortisol, which increases blood glucose and reduces insulin sensitivity. Plus, harder exercise spikes you more than softer exercises.

Things like walking and aerobics can actually lower your glucose, especially when fasting. (Use this to your advantage to prevent a spike after meals!)

3. Stress‍

Your body can’t tell the difference between physical threats and mental stress, so you release a bunch of fight-or-flight hormones that jack up your glucose when stressed.

Acute stress (like hearing really bad news, or a family emergency) can cause a spike in the short term. Chronic stress (like financial worries or a toxic relationship) can elevate your overall glucose levels via insulin resistance.

‍4. Heat exposure (showers, saunas, etc)

Any prolonged heat will increase your blood flow to the skin, which increases the concentration of interstitial glucose that your CGM measures.

5. Not exercising after a meal‍

Moderate exercise increases your sensitivity to insulin while burning off blood sugar to fuel your movement. If you don’t move after eating, you’re kind of asking for a spike.

‍6. Not getting enough sleep‍

Sleep loss itself won’t spike your glucose. But not sleeping enough is strongly associated with insulin resistance and a slower metabolism, both of which will result in higher-than-normal glucose response. (Even to healthy meals.)

‍7. Eating late‍

There’s a reason why insulin sensitivity is highest in the morning and lowest at night…you’re not designed to eat at night! You’re more insulin resistant at night, so any carbs you eat past 7:00 pm are more likely to spike your glucose.

‍Things that can CRASH your glucose‍

Most of the glucose game is spent trying to lower your blood sugar. Because it’s not low glucose that causes obesity and metabolic illness…it’s definitely high glucose. But sometimes you might look at your glucose and feel worried because it dipped out of the blue. Here are some possible reasons.

‍1. You spiked‍

Your body can actually overcompensate the insulin response for carbs and crash your glucose.

Whether you overcompensate and by how much depends on the type/quantity of your meal and also on your unique metabolic makeup.

You really want to avoid this type of low because your body triggers crazy-strong cravings that lead to the wrong kind of foods—and, subsequently, more spikes and dips.

‍2. Cold exposure (baths, showers etc.)‍

Experiencing cold can lower your glucose both actually and artificially. Cold exposure increases metabolism (so you burn fat for heat), and it reduces blood flow to your extremities, which leads to less blood flow near the skin, and consequently, a lower interstitial glucose concentration.

3. Alcohol‍

Alcohol is a toxin that must be filtered out of the body by the liver. And the liver wears many hats, one of which is ‘blood glucose regulator.’ When your liver is busy filtering out toxins, it can’t wear its glucose regulator hat at the same time.

So blood sugar can drop, then spike, then drop, then spike.

This happens because the liver stops releasing sugar from stored glycogen, which necessarily lowers glucose. Then you get cravings from the low.

‍4. CGM inaccuracy‍

You’ve definitely heard this before, but CGMs aren’t 100% accurate.

Several factors influence a CGM’s accuracy:

  • the first day and last day of a sensor’s lifespan
  • sleeping on the CGM
  • (uncommon) factory defects

If you see unusual lows, don’t be worried. (Note: Veri is not a medical device and shouldn’t be used to diagnose medical conditions like hypoglycemia.)

If the unusual lows persist, contact our team and ask for a replacement.

*Don’t remove your sensor if you think it’s defective! Our team can’t give you a replacement until they’ve troubleshooted the device when it’s connected to you.

5. Fasting

You’re usually not going to have big crashes when fasting—you don’t have enough insulin during a fast for that to happen. But it’s perfectly normal for your glucose to drop gradually as the day progresses.

Your liver and muscles only have so much energy stored up for fasting. And once you’ve burned through all that glycogen, your liver starts producing sugar from proteins and fats in a process called gluconeogenesis. This process is pretty inefficient, and it doesn’t produce enough sugar to keep your glucose at optimal levels.

In conclusion

Spikes and crashes can happen out of the blue and seemingly for no reason. But usually there’s a culprit. Food, exercise, and sleep play a big part. Ditto for hot and cold exposure. But if you really, really want to know what spikes your glucose…you’ve got to get a CGM and see for yourself



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Further reading