Are Dark Keto Strips Dangerous? Do They Mean You're Dehydrated?

2017-08-05

Four minutes answering one common worry. Someone gets a dark strip, worries that their ketones are dangerously high, and the reply I heard most was "you're dehydrated, drink more water." This was my answer to both.

In this video

[0:00] In my opinion, no, dark strips aren't dangerous. The only way I knew of, from the reading I'd done, for ketones to get dangerously high involved kidney problems, or diabetes (video GojQvo_2GS0).
[0:30] "You're dehydrated" is the usual reply, and then the person insists they've been drinking plenty. So check the urine itself.
[1:00] Clear to pale means hydrated; if it was clear you may even be over-hydrated. If the urine was very dark, that probably explains a very dark strip.
[1:30] Strips show fewer ketones over time. By month three to six, some people don't show positive at all while definitely in ketosis, which is why longer-term people move to blood meters.
[2:00] Strips are a cheap beginner check: reactive or not. The shade doesn't tell you much.
[2:30] If you're older or have health history, get baseline values from your doctor so you can compare at six months or a year.
[3:00] Many type 2 diabetics have some subclinical kidney issue; talk to your doctor when you start.
[3:30] Otherwise a dark strip most likely means early fat adaptation, with acetoacetate spilling into the urine.

The line that holds up: look at the cup, not the strip

I'd still lead with the simplest check. You already looked at your urine to dip the strip. If it was pale yellow, "you're dehydrated" probably isn't the answer, and the dark strip is most likely just ketones spilling over before your body uses them well (video GojQvo_2GS0).

And the strip colour is a weak signal. I said reactive or not is the useful part; the shade isn't (video GojQvo_2GS0). The evidence page has a review covering how blood and urine ketone monitoring works and how levels differ between ketosis and ketoacidosis (Laffel 1999). Urine strips pick up acetoacetate, as I explained in the three-ways-to-test video (video 8wOheKcBEd8); the liver makes acetoacetate, BHB and acetone (StatPearls, Ketogenesis). So a strip sees one of the three. More in urine strips and blood meters.

Drill-down: ketosis vs ketoacidosis, and who it matters for

The real fear behind "is my strip dangerous" is ketoacidosis. The clinical overview on the evidence page covers how nutritional ketosis differs from diabetic ketoacidosis (StatPearls, Ketogenic Diet). They're not the same state.

My caveat in the video is the part to take seriously. I said a dark strip in someone with diabetes or kidney issues could indicate a problem, and that type 2 diabetics especially should talk to their doctor when they start (video GojQvo_2GS0). I'd make it more specific now:

Type 1 diabetes: ketones mean something different for you. Don't run a keto diet off forum advice; your care team needs to be in on it.
Type 2 diabetes on medication: cutting carbs changes your blood sugar, and some diabetes drugs need adjusting. Ask before you start, not after a low.
Kidney disease or kidney risk: get the go-ahead and the labs first.
Older, or any health history: the baseline-labs idea from the video. Get numbers before, then compare at six to twelve months. See blood tests before keto.

I said "in my opinion" at the start of this video for a reason. I'm not a doctor, and strips are a beginner's tool, not a diagnosis.

Then vs now

Four days earlier I'd called ketone strips the one useful item in the "keto kit" (video DWI8qQl5BbY), and the same day as this one I made a video on three ways to test (video 8wOheKcBEd8). By 2019 I said you don't need to check your levels with a device; ketone monitors are optional (video 1JbK1_ClDmY).

This video sits between those. It already explains why: strips fade as you adapt, and the colour doesn't tell you much. If you're past the first month or two and losing, a pale strip isn't a reason to change anything. See strips not changing colour and do you need to test?.

Key points

In my opinion a dark strip isn't dangerous if you don't have diabetes and your kidneys are healthy (video GojQvo_2GS0).
Check urine colour before assuming dehydration. Pale yellow means you're probably fine on water. See urine colour.
Strips detect acetoacetate in urine, and they show less over months even while you're in ketosis.
Nutritional ketosis and diabetic ketoacidosis are different states.
Diabetes (either type), diabetes medication or kidney disease: involve your doctor before and during.
Older, or with health history: get baseline labs first.