I have rewritten my Ketostix PSA as a FAQ in hopes that it will be more useful to newcomers.
As always, let me know in the comments if you have any corrections or if you have questions that you think should be answered in this FAQ.
Are Ketostix recommended for monitoring a ketogenic diet?
No. They are not a reliable way of measuring ketosis. Misinterpretation of Ketostix results is one of the most common unnecessary causes of anxiety for ketogenic and low-carb dieters.
You can be perfectly successful on a ketogenic or low-carb diet without ever measuring ketones whether in urine, blood, or breath.
Can Ketostix be used to measure whether or not I am currently in ketosis?
No. You may be in ketosis even when the Ketostix show no ketones. Conversely, it is possible to see a positive Ketostix result even when you are not in ketosis.
Being in ketosis depends on having ketones in your bloodstream. Ketostix measures excess ketones in urine. There is no direct relationship between concentrations of ketones in urine and concentrations in blood. In fact, the ketones in urine are not even the same form of ketone as is found in blood.
- The ketones measured in urine are acetoacetate.
- The ketones measured in blood are ketone bodies or beta-hydroxybutyrate.
Why do my Ketostix show fewer and fewer ketones even though I've been following a ketogenic diet strictly for several weeks or more?
As your body becomes better adapted to the diet, it will excrete fewer and fewer excess ketones. This is because the body becomes better at using ketones for energy and because the kidneys filter fewer ketones.
Why do my Ketostix show a positive result even though I just ate a huge carbohydrate-filled meal?
Ketostix have a built-in time delay since it takes a while for your kidneys to form urine. At best, they show you that you may have been in ketosis at some point in the past.
Can MCT oil or coconut oil cause Ketostix to have a positive result?
Yes, if you consume coconut oil or MCT oil prior to using Ketostix, this may cause a temporary positive reading even if you would otherwise not be in ketosis.
What do the various shades of pink / purple mean? Is darker purple better than light pink?
The darker the color, the more excess ketones are being excreted. However, this tells you nothing about how many ketones are in your blood which is the only important factor. You may have ketones in your blood even if the Ketostix shows no result.
Once you have become fully adapted to a ketogenic diet, it is likely that Ketostix will show no ketones or only trace amounts. This is expected and is not a sign of being out of ketosis.
What are various factors that can influence Ketostix results?
Adaptation to the ketogenic diet will cause you to excrete fewer and fewer excess ketones over time even though you are still have high levels of ketones in your bloodstream.
Drinking more water will dilute ketones in urine.
Exercising may cause you to excrete fewer excess ketones or more excess ketones. This has no bearing on whether or not you are actually in ketosis.
Drinking MCT oil or coconut oil may cause a temporary positive Ketostix result.
Expired Ketostix or Ketostix exposed to dampness (for example, in a bathroom) may not work properly.
Where can I read more about what Ketostix actually measure?
Read this article which is based on pages 164 and 165 of Volek and Phinney's excellent book The Art and Science of Low Carbohydrate Living
Alternatively, pick up Volek and Phinney's book. It contains much useful information for the ketogenic and low-carb dieter and for those who are simply curious about how human metabolism works.
Given that Ketostix are unreliable, what are some signs that I am in ketosis?
If you are restricting your carbohydrate to 20 grams or less per day, then you will be in ketosis within 24 hours regardless of whether or not you show any signs. This is how the human body works.
Here are some typical signs. Not everyone shows all signs and some people show no signs at all.
- a sense of well-being
- reduced hunger or reduced appetite
- loss of significant water weight within a week
- strong-smelling urine
- bad breath (even though you just brushed your teeth)
- frequent peeing in the first few days of restricting carbohydrate
- fatigue, headaches, brain fog, or muscle cramps if you do not supplement sodium, potassium, and magnesium as described in the Keto FAQ – /r/keto/wiki/faq#wiki_how_do_i_replenish_electrolytes.3F
- feel like you have more energy than usual (although possibly less energy at first)
- better sleep (although worse sleep happens for some)
- persistent metallic taste in your mouth (only a small percentage seem to experience this)
- altered body odor
Is there a way to measure ketosis directly?
If you have a medical condition that makes monitoring blood ketone levels necessary or if you are simply very curious with spending money in hand, you may be interested in purchasing a ketone blood meter and test strips for measuring beta hydroxybutyrate in your blood. The ketone blood meters tend to cost $20 to $40. Each test strip costs somewhere between $2 and $5.
There are a few meters to choose from.
Most use one of the first two listed (Precision Xtra or Nova Max Plus). Some say that the Precision Xtra is the more accurate of the two. I've found that readings from these two track fairly closely with each other. The Nova Max Plus has cheaper test strips.
Another option is the Ketonix Sport breath meter. This meter measures acetone in the breath. It does not require test strips. Acetone forms when acetoacetate spontaneously breaks down to acetone. According to Volek and Phinney (page 165 of The Art and Science of Low Carbohydrate Living), it should be linearly correlated with blood ketones. In practice, it is not as accurate as the blood meters in part because it is difficult to breathe in the same way every time you test.
Note that the Ketonix Sport model measures with more granularity than the regular Ketonix model. When measuring ketones on a ketogenic diet, the Sport model gives more precise results.
If I am kicked out of ketosis, how long does it take to be back in it?
It takes less than 24 hours to re-enter ketosis. The liver is able to store only 100 grams or so of glycogen. Once it uses all of this glycogen, it begins burning fat. As a side-effect of burning fat, it produces ketones.
Note that being in ketosis is not the same thing as being keto-adapted. Fully adapting to a ketogenic diet can take from four to twelve weeks of being in ketosis consistently. Once you are fully adapted, your brain relies primarily on ketones for energy and your muscles rely primarily on fatty acids for energy.
If you go in and out of ketosis on a regular basis, you may never become keto-adapted.
Read this article for more information on ketosis and keto-adaptation.