Veri Logo

Things That Spike (and Crash) Your Blood Sugar

Blood sugar spikes are harmful to your health, but they can be avoided. Here's what spikes your glucose:

If you’re reading this, you probably know that 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.

So… What are the worst offenders that you should know about?

Things that can spike your glucose:

Couple housekeeping items here, before we dive in:

  • 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

1. Food

First and most obvious, food can spike your blood sugar. 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 piece of fruit or a veggie/grain dish.

The game is to see which foods don’t spike you, and to stick with those foods for the most part. (Gotta have a CGM to do this!)  

2. Exercise

Hard workouts trigger stress hormones like cortisol, which increases blood glucose and reduces insulin sensitivity. (Double whammy.) 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

Food and exercise are supposed to be married to each other. When your caveman ancestors ate piles of apples in the fall, you can bet they weren’t sitting on their caveman butts and watching TV afterward.

They moved, and so should you.

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

Okay, 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!

Cave people lacked the fridges and bags of chips that make late-night munching so easy for us. When they were hungry, they waited till the morning light so they could see well enough to hunt or forage.

Long story short:

You’re more insulin resistant at night, so any carbs you eat past 7:00 pm are likelier to spike your glucose.

Things that lower 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's why:

1. You spiked

This might seem like nonsense at face value, but your body can actually overcompensate the insulin response for carbs and crash your glucose.

Whether you overcompensate at all or by a lot 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 food and hey, more spikes and dips! (and spikes and dips and spikes and dips)

2. Cold exposure (baths, showers etc.)

Experiencing cold can lower your glucose both actually and artificially.


Yes, cold exposure increases metabolism (so you burn fat for heat), and it reduces blood flow to your extremeties, which leads to less blood flow near the skin, and consequently, a lower interstitial glucose concentration.

3. Alcohol

We all love alcohol, and it makes the game of life more fun to play. But it doesn’t really jive with the glucose game.

See, 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 being the fun police/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. And presto: you’re riding the glucose rollercoaster.

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.(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 your 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 fed levels. Hence, the slow glucose slide.

Stuff we say at the end

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



Get started with Veri today


Further reading