What’s the Best Time to Test Blood Ketones? (And How Often)

What's the best time to test ketone levels? Bottom line… these blood ketone strips are EXPENSIVE - we don’t want to be wasting them.​

There are several times during the day when you’re going to get misleading readings.

By the end of this article you’re going to know

  1. When you should be testing
  2. When you shouldn’t be testing
  3. And how often you need to be testing in order to get an accurate picture of your ketone levels.

Lets get started…

Table of Contents

I’ve never been a big tester of ketone levels.

When I went through my period of rapid weight loss back in 2016 I didn’t check ketones once. I didn’t need to – I was consistently losing weight and that was my goal.

There is this myth in the “keto diet” world that and that we should be aiming for high ketone levels all the time – and it’s simply not true, in fact, it often leads to overconsumption of fat, underconsumption of protein and is counterproductive.

I’ve made a separate video that deconstructs this myth and you can check that out here….

A lot of keto websites/youtube channels are sponsored by the manufacturers of ketone meters. I’m not. So I’m not going to tell you that you should be testing all the time. Because it’s just not true.

Testing has its place.

Someone Testing blood ketoned

Testing does have its place and it can be useful, typically for overcoming problems, so if you are testing then measuring blood ketones is by far the most accurate way to check ketone levels.

I know some people who find testing their ketone levels reassuring.

It provides some sort of accountability to the data and they know they’re on the right track.

Also, if like me, you’re a bit of a data geek it can be quite fun to track these things!

But whilst the ketone meters themselves are often relatively cheap, the test strips themselves are still quite expensive.

We don’t want to be wasting them, testing more often than we need to or testing at times of day where we are going to get a misleading reading, so we should really know when is the best time to test blood ketones.

Falsely Low Readings

There are several times during the day where you’re going to get falsely low readings.

The first time you should avoid testing is first thing in the morning and that is due to

The Dawn Effect

best time to test blood ketones

This is a normal physiological process that happens in all of us.

In the early hours of the morning there is a release of a number of hormones (cortisol, adrenaline, growth hormones etc), and this is part of the body’s normal circadian rhythm.

It promotes the release of glucose into the bloodstream which helps prepare you for the day ahead.

Diabetics may notice a spike in their blood glucose levels if they test first thing in the morning.

Non-diabetics should not see a rise, as the body effectively compensates by releasing insulin.

This rise in blood glucose will cause a dip in the production of ketones and testing first thing in the morning may give you a lower reading than you may have been expecting and it’s all due to the dawn phenomenon.

So the first time to avoid testing your ketone levels is first thing in the morning.

Wait at least an hour…

Directly after eating

The second time you should avoid testing is directly after a meal.

Even a low carb meal will cause some insulin to be released by the pancreas; it is not uncommon to see a temporary dip in blood ketones levels at this point.

Ketones often quickly recover over the next few hours, but not in an entirely predictable way. It will vary depending on the meal.

As a side note:

Some people do like to see the response their meals have on their ketone levels and may test on a schedule such as

  • Before Meal
  • 30 mins
  • 1 hour
  • 2 hour

This can be quite interesting for a data geek like me to see my body’s response (both ketones and glucose actually) but it doesn’t tell us a lot about the long term stable levels of ketones that our bodies are achieving.

So do it if you’re curious, but not for any other reason.

After exercise

person exercising in a gym

The third time of day you should avoid testing is directly after exercise. Ketones are being used by the body for energy, and anything that causes them to be used faster… e.g. exercise will cause a temporary lowering of ketone level that will misrepresent your longer-term levels.

Again, by all means, test for curiosity but don’t get misled when the levels drop.

What is the best time to test blood ketones?

I typically recommend that the best time of day to test is before main meals. Typically lunch and dinner. For me, that is typically 12pm and 7pm which fits in with my normal 16 – 8 pattern of fasting.

Checking Before Lunch

This gives plenty of time for the dawn phenomenon to pass. – and I typically work out in the morning too.

If you typically skip breakfast (like many low carbers do) then it will be approximately 16 hours since your last meal. If you’ve not achieved a stable level of ketones by this time… you’re not in ketosis.

If I had to test just once a day… it would be before lunch.

Check Before Dinner

Plenty of time for you to achieve stable levels of ketones after lunch.

But not if you’ve just exercised.

You may wish to consider testing before bed if for example you often work out before your evening meal.

Twice a day will give you a good idea if things are stable. Adding in a 3rd testing point won’t really add much to your data.

If you’re going to be testing on a regular basis, you’re going to want to find a pattern that works for you and your particular lifestyle. Just make sure you avoid the common mistake times that I’ve mentioned above.

Work out what works for you and stick to it!

Be sure to check out my video where I discuss optimum ketone levels. Please don’t get caught in the trap of chasing high ketone levels… it doesn’t matter anywhere near as much as you might think!

You may also find it useful to check out my video on simply monitoring your symptoms to check you’re in ketosis.