Doing Keto? Consider Buying a Blood Glucose Meter

The amount of glucose in your blood at any given time can give you valuable insights into how your body is reacting to the food you eat. If you’re doing a keto-based diet, the data you get from a blood glucose meter will help you optimize your eating for maximum weight loss.

The premise of a keto-based diet is simple: keep the carbs as low as possible so that your body is forced to get glucose (energy) from fat, rather than carbs. Any sort of glycemic reaction could cause a weight-loss stall for several days.

Not sure what a Keto diet is, or want to learn more about it? I talk about what a keto diet is, and the pros and cons of this approach in this blog article. 

What is a glycemic reaction?

In short, a glycemic reaction is what happens when you eat carbs. It’s a fancy name for an even fancier process. Effectively, when you eat carbs, your body produces a hormone called insulin which is responsible for delivering the glucose (the energy from the carbs you just ate) to the muscle cells in your body.

In a keto-based diet, you want to avoid the production of insulin at all costs. Not because insulin itself is bad, but because it means you’ve short-circuited the keto process by eating too many carbs and allowing your body to get energy from carbs rather than fat. If this happens, it can take days to “reset” your body back into ketosis.

In short, if you are doing a keto-based diet and your blood glucose levels spike, you screwed up.

How to measure your blood glucose level

Get yourself a blood glucose meter!

You can buy a blood glucose meter from any pharmacy in the $20-$40 range. The test-strips come in packs of 100 for around $25. (that is $0.25 each if you’re bad at math). Here’s a link on Amazon to a glucose meter kit that’s perfectly adequate.

This is the same device that a diabetic would use to check their blood sugar levels. They are simple to use and super portable. The process involves pricking your finger to take a very small blood sample and inserting the sample into the meter. A few seconds later, voila, you’ve got your glucose level on a digital display.

What do the levels mean?

Under 60-65: WAY TOO LOW

Anything under about 60-65 is a sign that your blood sugar is too low. In this range, you will feel shaky, very hungry, and crave sugar and sweets. Your blood sugar can also hit this level if you’re experiencing a sugar crash. A sugar crash is that feeling you get after you’ve eaten a very sugary snack. If your blood sugar is in this level on a regular basis, you should see a doctor immediately. It’s a sign you may be hypoglycemic.


This is the sweet spot for a keto-based diet. It means your body currently has no real source of glucose available to it. A normal person should be in this range when they’re in a fasting state (as in, when they first wake up in the morning after having not eaten anything all night). A person doing a keto-based diet should aim to be in this range 24 hours a day, 7 days a week.

90-115: TOO HIGH

If you’re in this range, it’s a sign that you’ve eaten something that your body is reacting negatively too. You are producing insulin in small amounts (enough to prevent weight loss on a keto-based diet, and enough to knock you out of ketosis). Look back at what you recently ate, and narrow down what could have caused the reaction. Once you’ve figured it out, never eat that food item again!

115-180: GLYCEMIC

Your body is experiencing a full glycemic reaction. This is typically from eating large amounts of carbs or sugar. Without a doubt, you are no longer in ketosis, and your cells are now in “storage mode” meaning whatever else is sitting in your stomach is quite likely to be stored as fat. This is bad. Really bad. But you probably know what you ate that caused it. Also note that if your blood sugar level is in this range right after you wake up you should see a doctor immediately as it’s a sign that you may be diabetic, or pre-diabetic.

Over 180: SEE A DOCTOR

You may have a condition called “Hyperglycemia”. You should see a doctor as soon as possible.

How often should I measure?

I like to measure when I first wake up in the morning and 1-hour after I eat each meal or snack. Write the data down for about a week, noting what you ate, and what your blood sugar levels were one-hour after you ate it. After about a week or eating your normal “menu” you’ll have a good sense for the reaction your body is having to the food you eat, then you won’t need to measure anymore unless you change up your food choices.

Verify all new foods

If you introduce a new food into your routine, you should measure again 1-hour after eating it to ensure that it’s safe. Someimtes, food has hidden carbs or your body is not producing insulin when you eat it. You’d be surprised how often people on a keto-based diet struggle to lose weight, only to discover that they’re eating carbs and didn’t realize it. Or, more illusively, that they’re eating foods their body is reacting poorly to, and they didn’t know it.

One caveat

If you measure your glucose level immediately after a super intense cardio workout, you can expect a reasonably high reading, even if you haven’t eaten anything. This is the result of your body doing exactly what it’s supposed to do: converting fat to glucose and delivering it to muscles that need it. (Pretty cool, eh?)

In short…

I consider a blood glucose meter a critical item to have in any keto-toolbox.

  1. In the beginning, measure when you wake up, and 1-hour after each meal.
  2. Keep a detailed log of your results. (Time of day, reading, and what you ate).
  3. Aim to keep your blood sugar level in the 65 to 90 range at all times.
  4. If your number goes above that, narrow down what food caused it and/or eliminate it from your diet.