Ketone Strips: Do They Verify Ketosis For Keto Dieters?

Ketone strips are a popular tool for keto dieters to check if they have entered ketosis, a natural metabolic state where the body burns fat for fuel. They are thin paper strips that detect the presence of ketones in urine and change colour accordingly. While they are a cheap and convenient way to test for ketosis, they may not be entirely accurate, especially for long-term keto dieters, as the body gets better at using ketones for fuel and fewer are excreted in urine. For a more accurate reading, keto dieters can opt for blood ketone meters or ketone breath analysers, though these are more expensive.

What are ketone strips?

Ketone strips, also known as keto strips or ketone test strips, are small, thin paper or plastic strips used to measure the level of ketones in your urine. They are a cheap, non-invasive, and convenient way to test for ketosis, especially for those on the ketogenic diet.

Ketone strips were originally developed for people with type 1 diabetes to determine if they are at immediate risk of diabetic ketoacidosis, a potentially life-threatening condition. Diabetic ketoacidosis is a medical emergency that may be fatal and is common in people with type 1 diabetes but can also develop in people with type 2 diabetes.

Ketone strips contain an absorptive pad on one end that reacts with your urine. The pad contains a chemical reagent that changes colour in the presence of acids such as ketones. The darker the colour, the higher your ketone levels. The strips typically measure the presence of acetoacetate, the second most abundant ketone, in your urine.

To use a ketone strip, you can either urinate directly on the strip or immerse it in a urine sample. After 15 seconds to a minute, the pad will change colour. You then compare the colour to a chart provided with the test kit.

Ketone strips are most accurate when you are just starting a ketogenic diet and your body is still adapting. As your body gets used to the diet and becomes more effective at using ketones for fuel, fewer unused ketones will be excreted in your urine, which may result in a lighter colour on the strip even though you are in ketosis.

While ketone strips are a convenient way to test for ketosis, they may not always be accurate. Blood ketone meters and breath ketone analysers are more expensive but provide a more accurate measurement of ketone levels.

How do they work?

Ketone strips are usually small strips that people use when they're on the ketogenic diet to measure the level of ketones in their urine. They are made from a special type of paper that contains chemicals that change colour when they come into contact with ketones in the urine. The strips have colour codes that indicate the level of ketones in your urine.

Here's how they work:

• Wash your hands.
• Pee into a small, clean container, then dip the test end of the strip into the urine sample. Alternatively, you can pass the end of the strip briefly through your urine stream.
• Wait for a few seconds (or as indicated on the test package) for the end of the strip to change colour.
• Compare the colour with the colour chart on the test package.
• Dispose of the urine testing strip. Then wash your hands.

The strips typically expire within three to six months of opening, so it's important to check the expiry date before testing.

It's worth noting that urine strips are not always accurate. Blood ketone levels are more accurate than urine ketone test strips. This is because urine strips only measure the unused or excessive ketones that the body doesn't use. As your body gets used to using ketones for fuel, it becomes more optimised in producing them, leaving less unused. Therefore, if you've been in a keto-adapted state for several months, a urine keto strip may indicate that your urine contains only trace amounts of ketones, if any, which can be misleading.

When is the best time to use them?

The best time to use ketone strips for keto is early in the morning on an empty stomach. This is because your body will have rested and cleared the food you ate the night before, giving you accurate results.

If you want to check your ketone levels day-to-day, it's best to stick to a specific time of day, like the morning or evening, for the best comparison. Testing at the same time every day will also help you to compare results.

If you are testing your ketone levels more than once a day, it's important to note that ketone levels can be affected by several factors, including:

• Adaptation: As your body adapts to the ketogenic diet, it becomes more effective at using ketones for fuel, meaning that fewer ketones will be excreted in your urine.
• Dehydration: One randomised controlled trial found a direct proportion between serum ketone concentration and the level of dehydration. The more dehydrated the subject was, the higher their ketone levels.
• Expired test strips: Check the expiration date of your urine test strips. Strips usually expire within three to six months of opening.

Are they accurate?

Ketone strips are a good tool to measure whether you're in ketosis during the first few weeks of going keto. However, they are not always accurate and there are a few reasons for this.

Firstly, ketone strips measure the number of ketones in your urine. However, any ketones that go unused by the body are excreted via urine. Therefore, urine strips only show the number of excessive ketones that the body couldn't use. This means that just because the level of ketones in urine is small, it doesn't mean that the levels in the blood are also small, or that you are not in ketosis. For this reason, blood ketone levels are a more accurate way of measuring ketosis than ketone test strips.

Secondly, as your body gets better at using ketones for fuel, fewer ketones will be excreted in your urine. This means that if you've been in a keto-adapted state for many months, a keto strip may indicate that your urine contains only trace amounts of ketones, if any. This can mislead people into thinking they're no longer in ketosis, which may not be the case.

Thirdly, the accuracy of ketone strips can be affected by hydration levels. If someone is drinking large amounts of water, it may dilute the urine to the extent that it affects the reading. On the other hand, if someone is dehydrated, then higher concentrations of ketones may be present. However, this is unlikely to be an issue for the average person consuming typical amounts of water.

Finally, the accuracy of ketone strips can be affected by time of day. A NIH study showed that the early morning or after dinner were the times of day with the highest and most reliably detectable levels of ketones.

Overall, ketone strips are a reasonably accurate and cheap way to detect someone's (approximate) state of ketosis. However, for someone attempting to enter therapeutic levels of ketosis, blood testing is a more accurate and valuable tool.

Are there any alternatives?

Yes, there are alternatives to using ketone strips to check for ketosis.

Blood Ketone Testing

Blood ketone testing is considered the most accurate way to confirm that you are in ketosis. This method measures blood ketone levels of beta-hydroxybutyrate (BHB), the most abundant ketone body. However, it is more expensive and invasive than urine testing, as it requires pricking your finger to draw blood.

Breath Ketone Testing

Breath ketone testing is another alternative to urine testing. This method measures acetone (Ace), the third and least abundant ketone, which is released in your breath. Breath testing is affordable, non-invasive, and convenient, but it is less accurate than blood or urine testing.

Lab Testing

Lab testing is the most expensive and highly accurate way to measure ketones in your blood. However, it is not practical for keto dieters as it requires visiting a lab or doctor's office, which is not feasible on a daily basis.

Frequently asked questions