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Urine Ketone Strips: How They Work and What the Colours Mean

Urine ketone strips change colour when acetoacetate, one of your three ketone bodies, spills into your urine, so a positive strip tells you ketosis is happening, but the shade tells you very little about how many ketones are in your blood.

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How a urine strip works

Your liver makes three ketone bodies from fat when carbohydrate is low: acetoacetate, beta-hydroxybutyrate (BHB) and acetone (StatPearls, Ketogenesis). A urine strip has a pad that reacts to acetoacetate. You pass the strip through your urine stream or dip it in a cup, wait the time on the package, and compare the pad to the colour chart.

The acetoacetate in your urine is not there for a purpose. It is the part your body did not use, which then passes out through the kidneys. KetoDick calls it a "spill" of ketones into the urine, not there by biological design, from the video (video 8wOheKcBEd8).

Strips do not read BHB, the main ketone in your blood. That is the job of a blood meter.

What urine strips cost

Urine strips are the cheapest way to test. KetoDick's figures:

Test Cost per test (his figures) Source
Urine strip About 7 to 15 cents video 8wOheKcBEd8, 2017
Urine strip About 6 cents video xyEZL0HuejI, 2017
Blood ketone strip About $3.50 to $4 same two videos

At those prices, he says you can test several times a day for under $30 a month (video 8wOheKcBEd8). Prices have changed since 2017, so check current ones.

What the colour does and does not mean

A strip answers one question well: is acetoacetate showing up in your urine right now?

What you see What it tells you What it does not tell you
No colour Little or no acetoacetate in this urine sample That you are out of ketosis, especially months in
Trace or light Ketones are being made and some are spilling How high your blood ketones are
Dark More acetoacetate in this sample That your blood ketones are high, or that you are dehydrated

The shade reflects ketones in your urine, not your blood. How concentrated your urine is also changes the shade. A sample after a lot of water looks lighter; a first-morning sample often looks darker.

KetoDick on this: he says the strips are accurate about urine ketones but not about blood ketones, and that a positive strip still means ketosis processes are running (video 8wOheKcBEd8). In 2017 he said any colour at all, including trace, most of the time is enough, and that the darkness does not matter (video xyEZL0HuejI).

Why strips fade as you adapt

Many people see dark strips in the first weeks and then watch them fade. This is expected.

  1. Early on, your body makes ketones before it is good at using them. More spills into urine.
  2. As you become fat adapted, your body uses more of the acetoacetate it makes.
  3. Less spills, so the strip gets lighter, even if your blood level has not changed.

KetoDick says that by month three to six, strips sometimes stop showing positive even though the person is still in ketosis (video GojQvo_2GS0). In another video he gives three to six months, and says that if you are still eating the same way and feel the same, you are probably still in ketosis (video xyEZL0HuejI).

A fading strip is a sign of adaptation, not failure. See Ketone strips not changing colour.

Dark strips and dehydration

A common reply to a dark strip is "drink more water." Dehydration can make a strip darker, because concentrated urine holds more of everything. But a dark strip on its own does not prove dehydration.

Check the urine itself instead:

Urine colour What it suggests
Clear You may be drinking more than you need
Light pale yellow Adequately hydrated
Normal yellow for you Probably fine; a dark strip likely means early ketosis
Dark amber Likely dehydrated; this can explain a very dark strip

This table follows KetoDick's advice in videos 8wOheKcBEd8 and GojQvo_2GS0. For more on fluids, see How Much Water on Keto? and Urine colour and hydration.

KetoDick on this: in his opinion, dark strips are not dangerous for someone without diabetes and with healthy kidneys. He says a healthy person with normal kidney function cannot reach a dangerous ketone level through diet alone, and that dark strips in weeks two and three are normal transition spill (videos GojQvo_2GS0, 8wOheKcBEd8). The difference between nutritional ketosis and ketoacidosis is covered in Ketosis vs Ketoacidosis.

How to use strips well

If you choose to use strips, keep it simple:

  1. Use them as yes-or-no. Positive means ketones are being made. Do not chase a darker colour.
  2. Test at roughly the same time of day if you want to compare days, since urine concentration changes.
  3. Use them to check a suspect food. If a strip that is usually positive goes blank after a new sauce or snack, look for hidden carbs.
  4. Expect them to fade. After a few months, a blank strip is common and does not mean you stopped.
  5. Store them as the package says. Strips exposed to air and moisture can stop reacting properly.

KetoDick on this: in 2017 he called strips the one useful item in a "keto kit," because they give biofeedback on which foods cause problems (video DWI8qQl5BbY). His later view on whether to test at all is on Do You Need to Test Ketones at All?.

When a dark strip is a doctor question

For most people a dark strip is not a medical event. It can be one if you:

See Who Should Talk to a Doctor Before Starting Keto.

Last verified: 2026-10-31