Testing for Ketones: Positive Urine Test and Negative Blood Test?

(Whitney) #1

I know someone who had a negative/undetectable level of blood ketones at the same time she had a positive ketone reading from a urine strip. These were both at-home tests taken within a couple of minutes of each other by someone who has been keto several months. Why would this happen?

My guess is that the ketones in the urine had spilled over into the urine a few hours before, when the blood may have also had ketones. But then, by the time she urinated, the blood ketones had fallen to an undetectable level, maybe because of exercise or eating a few too many carbs (from something like having too many nuts) or something else that would have used them up, but the urine ketones were still there waiting to be expelled in the urine. The person that this actually happened to had a different interpretation: she thought it was because her body was not adequately converting her ketones from the type found in urine (acetoacetate) to the type found in the blood (beta-hydroxybutyrate). She assumed that because she is currently pregnant that her body is not making beta-hydroxybutyrate anymore. I can’t find anything in the scientific literature to support her assumption. In fact, I found a few papers showing that beta-hydroxybutyrate was elevated in pregnant women in certain conditions (diabetic, when fasting during Ramadan), so it doesn’t make sense to me for her to blame these results on pregnancy.

So, what does everyone think? Why would a woman (pregnant or not) take a urine ketone test and a blood ketone test at the same time and have the urine test show up highly positive and the blood test come back negative?

(Erica Ramirez) #2

A not so great scenario is gestational diabetes. Can she test her urine for glucose? If she’s having ketones and glucose spilling in her urine she talk to her doctor.

(J) #3

How pregnant is she? The most common cause of urine ketones in pregnancy is dehydration. The second half of pregnancy is actually closer to a ketogenic state in that the fetus gets the first pass of glucose metabolism and mom will burn fat if there is not enough in the second pass. Is she eating keto during the pregnancy?

(Katie the Quiche Scoffing Stick Ninja ) #4

There are too many variables
How long has she been Keto
Is she fat adapted
Was she in ketosis then ate something which kicked her out and then tested?

You can certainly be wasting ketones in urine, and not have any within your blood because you’re not fat adapted yet and your body has not learned to use the ketones it’s producing?

(KCKO, KCFO 🥥) #5

The urine strips are best for seeing your level of dehydration. If deep purple, drink lots of water. Even the Atkins Co. stopped recommending them about a decade ago. They never worked for me, I used a breathalyzer instead. The urine strips never showed me in ketosis, because I drink water all the time. Also if you are using those ketones, they are not getting expelled in your urine.

(You've tried everything else; why not try bacon?) #6

Another, unrelated possibility: one of the batches of strips could be bad or out of calibration.

(KCKO, KCFO 🥥) #7

Because Dr. Atkins had recommended them in his books, I tried three batchs, elcheapos from Amazon, then ones from two local pharmacies near me on the Front Range, I had thought about a bad batch but I got the same bad results with all of them. So unless I have had excellent ketone useage from day one, they didn’t work for me. Being a bread addict, I knew I wasn’t going into ketosis then, only weight I lost was water originally. Those 3 sources where spread over about 3 months. I thought I was doing something wrong, but finally learned it was just the fact I didn’t get dehydrated like some do.
The elcheapo breathalyzer worked right out of the box, I had done my homework and knew how to breath for a valid result.