Because most urine tests measure acetoacetic acid, and not the most commonly found beta-hydroxybutyrate acid, it is possible to have ketones present and get a negative urine test result.
Further, it's also possible to have high levels of beta-hydroxybutyrate acid, get a negative urine ketone test result, but to have the test turn positive as the ketosis improves, due to the tests' measuring acetoacetic acid and not beta-hydroxybutyrate acid. 
The following medications and/or problems with urine samples can produce false negative or false postive results when testing urine for ketones.
See Urine testing stix-Reading Results for examples of ketodiastix and ketostix color charts.
Possible False Urine Ketone Test Results--Drugs and Supplements
|Valproic Acid (brand names)|
Divalproex Sodium 
|Positive. Common use:|
Treatment of epilepsy.
|Cefixime/Suprax ||Positive with nitroprusside-based|
urine testing. Common use: Antibiotic.
|Levadopa Metabolites ||Positive with high concentrations .|
|Tricyclic Ring Compounds ||Positive. Common use:|
Treatment of depression.
other drugs with free sulfhydryl groups 
|Positive. Captopril Common use:|
(high blood pressure),
various heart conditions,
preserving kidney function
in diabetic nephropathy .
Pyridium, Geridium, Pyridiate, or Urogesic .
|Positive. Common use:|
Urinary tract infections.
|Glucocorticoids/Steroids ||Positive. Common use:|
Allergies, replacement therapy, others.
|Vitamin C Supplements .||Negative.|
Possible False Urine Ketone Test Results-Other Reasons
|Pigmented Urine ||Positive-|
Any other color except yellow or clear 
May be the result of other disease processes.
|Dehydration ||Positive or negative|
lack of fluids can concentrate ketones
|samples with high specific|
gravity and low pH 
|Old Urine Sample ||Negative-|
ketones can evaporate rapidly.
|Older opened test strip container ||Negative|
If your pet is taking any type of vitamin supplements, it should be noted on his or her medical records. Knowing that he/she is using them means being able to factor them into interpretations of test results.
- ↑ Patient.co.uk-Ketones-False Positives, False Negatives. Patient.co.uk.
- ↑ Valproic Acid. NetDoctor UK.
- ↑ Suprax/Cefixime. RXList.com.
- ↑ Levadopa. Drugs.com.
- ↑ 5.0 5.1 5.2 Sine, Cheryl S, et. al. (2003). Urinalysis Dipstick Interpretations-Ketones. University of Georgia.
- ↑ 6.0 6.1 6.2 Hanas, Ragnar. Measuring Ketones in Blood. Children With Diabetes.
- ↑ 7.0 7.1 Taylor, Judith A. (November 2006). Clinical Lab Medicine Harvesting The Gold: Interpretation and Techniques of Urinalysis. District of Columbia Academy of Veterinary Medicine.
- ↑ Tricyclic Antidepressant. Wikipedia.
- ↑ Captopril. Wikipedia.
- ↑ 10.0 10.1 Ketone Test Explained. Diabetes Explained.
- ↑ Phenazopyridine. Merck Manuals Online.
- ↑ Ketones. Medline Plus.
- ↑ Precision Xtra Blood Ketone Test Strips. Abbott Diabetes Care.
- ↑ 14.0 14.1 Hanas, Ragnar. Measuring Ketones in Urine. Children With Diabetes.
- ↑ Taylor, Judith A. (November 2006). Urinalysis: What Is Abnormal?. District of Columbia Academy-Veterinary Medicine.
- ↑ Dehydration and Ketosis. North American Veterinary Conference (2003).
- ↑ Preanalytical Variables in Urine Testing. BD Diabetes (2006).
- ↑ Consequences of inappropriate urine specimen storage. Chronolab.
- ↑ Precision Xtra-When is it Recommended to Test?. Abbott Diabetes Care.
- Urine Ketones Cornell University