Keto strips measure whether your body is producing ketones, the molecules your liver makes when it burns fat for fuel instead of carbohydrates. The most common type is the urine dip strip, which changes color based on the ketone concentration in your urine. You dip the strip, wait for it to develop, and compare the color to a chart on the bottle. The whole process takes about a minute.
Three Types of Keto Strips
There are actually three ways to test ketone levels at home, and each one detects a different type of ketone molecule.
- Urine strips are the cheapest and most popular option. You dip a test strip into a urine sample (or hold it in your stream) and wait for it to change color. These strips detect a ketone called acetoacetate.
- Blood ketone meters work like a blood glucose monitor. You prick your finger, apply a drop of blood to a test strip inserted into a small meter, and get a digital reading in seconds. These measure beta-hydroxybutyrate, the most abundant ketone in your bloodstream and the most accurate marker of ketosis.
- Breath meters are handheld devices that detect acetone in your exhaled breath. They’re reusable and don’t require any consumable strips, but they tend to be less precise for tracking specific ketone levels.
Most people searching for “keto strips” are looking for the urine version, so that’s what the step-by-step instructions below focus on. Blood meter instructions follow.
How to Use Urine Keto Strips
The process is simple, but a few details matter for getting a reliable reading.
Collect a urine sample in a clean, dry cup. Remove one strip from the bottle and reseal the cap immediately. Dip the strip’s test pad into the urine for one to two seconds, then pull it out and hold it horizontally. Holding it flat prevents urine from running along the strip and distorting the color. Wait the amount of time specified on your bottle’s label, usually 15 to 40 seconds depending on the brand. Then compare the color of the test pad to the chart printed on the bottle.
The color scale typically runs from beige or light pink (negative or trace ketones) through darker pinks and into deep purple or maroon (high ketone concentration). A light-to-medium pink usually indicates you’re in a state of nutritional ketosis. You don’t need to aim for the darkest color on the chart. In fact, very dark readings can sometimes just mean you’re dehydrated rather than deeply ketotic.
How to Use a Blood Ketone Meter
Blood meters cost more upfront, and each test strip is individually more expensive than a urine strip. But they give you a precise numerical reading rather than a color you have to interpret by eye.
Insert a ketone-specific test strip into the meter (these are different from glucose strips, even if you use the same device for both). Load a fresh needle into the lancing pen. Prick the side of your fingertip, which is less painful than the pad. Squeeze gently to form a blood drop. Blood ketone strips need a slightly larger drop than glucose strips do, so don’t rush it. Touch the tip of the test strip to the blood droplet and let it absorb. The meter displays your result in a few seconds, measured in millimoles per liter (mmol/L).
What Your Results Mean
For blood readings, healthy people who eat a standard diet typically have ketone levels below 0.5 mmol/L. Once you enter nutritional ketosis, which is the goal on a ketogenic diet, your levels generally fall between 0.5 and 3.0 mmol/L. Readings above 3.0 mmol/L are uncommon on a standard keto diet and worth monitoring. Levels above 5.0 mmol/L can signal diabetic ketoacidosis, a dangerous condition that primarily affects people with type 1 diabetes.
For urine strips, you won’t get a precise number. Instead, you’re reading a color gradient. Trace-to-small levels (light pink) suggest your body has just begun producing ketones or that you’re well hydrated and diluting the sample. Moderate levels (medium pink to light purple) typically indicate you’re in ketosis. Large levels (dark purple) can reflect genuinely high ketone production, but they can also result from concentrated urine when you haven’t been drinking enough water.
For breath meters, readings are measured in parts per million (ppm) of acetone. Research on healthy adults following a ketogenic diet showed average breath acetone rising from about 0.7 ppm to 2.5 ppm after 12 hours of ketogenic eating. Higher readings develop over days and weeks of sustained ketosis.
When to Test for the Most Accurate Reading
Your ketone levels fluctuate throughout the day based on what and when you last ate. Testing after a fasting period, or at least three hours after a meal, gives you the most consistent snapshot. Many people test first thing in the morning before eating, though there’s no single “correct” time.
What matters more than the specific hour is consistency. Pick the same time each day so you’re comparing apples to apples. If you test at 7 a.m. one day and right after lunch the next, the swing in readings will tell you more about meal timing than about whether your diet is working.
Why Urine Strips Can Be Unreliable
Urine strips have a real limitation that’s worth understanding. They detect acetoacetate, but the primary ketone circulating in your blood is beta-hydroxybutyrate. As your body becomes more efficient at using ketones for fuel over weeks of keto eating, it converts more acetoacetate into beta-hydroxybutyrate. Your urine strips may show lower readings even though your blood ketone levels are stable or rising. This is why long-term keto dieters sometimes see their urine strips fade to near-negative, which can be discouraging but doesn’t mean ketosis has stopped.
Hydration plays a big role too. If you’re dehydrated, your urine is more concentrated and the strip reads darker. If you’ve been drinking a lot of water, the strip may barely change color even though your blood ketones are solidly in the ketosis range. Certain medications and high-dose vitamin C supplements can also cause false positive readings on urine strips.
Blood meters avoid all of these issues because they measure the dominant ketone directly in your bloodstream. If you want reliable tracking over months, a blood meter is the better investment. Urine strips work well for the first few weeks of a keto diet when you mainly want confirmation that your body has shifted into ketone production.
Storing Your Strips
Both urine and blood ketone strips are sensitive to environmental conditions. Keep them in a cool, dry place away from direct sunlight and heat. Do not store them in the refrigerator, because condensation inside the container can damage the reactive chemicals on the test pad. Always reseal the bottle or foil wrapper immediately after removing a strip.
Urine strips expire six months after the bottle is first opened, regardless of the printed expiration date on the label. If you test infrequently, write the date you opened the bottle on the label so you know when to replace them. Expired strips can give inaccurate readings, usually reading lower than your actual ketone levels.