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Ketones in urine test strips are plastic strips with a chemical pad that changes color when ketones are present in a urine sample. In the FDA’s 510(k) review of one over-the-counter ketone strip, the device is described as providing “qualitative and semi-quantitative detection of ketone (acetoacetic acid) in urine,” read by eye against color blocks on the bottle label. This page explains how the pad works, how ketone-only strips differ from multi-parameter strips (including urine pH strips), and which tested limits the regulatory record documents.
This page describes products and general use; it is not medical advice.
Who uses it: people who test urine at home (for example people with diabetes or people following low-carbohydrate diets, the OTC users named in the FDA summary), clinic staff who stock urinalysis supplies, and students learning urinalysis.
What ketone urine test strips are
A ketone urine strip is a single-use reagent strip: a plastic handle carrying a reagent pad. The FDA summary for the ACON On Call / Healthy Me Ketone Reagent Strips for Urinalysis (K170587) states that ketones are normally not present in urine, and that identifying them is used in the diagnosis of acidosis or ketosis and for monitoring patients on ketogenic diets. The same summary says “This product is not intended for the management of diabetes.”
The regulation that defines the device type, 21 CFR 862.1435, describes a ketones test system intended to identify ketones in urine and other body fluids, used in diagnosing and treating acidosis and ketosis and in monitoring ketogenic diets and patients with diabetes. It is a Class I device, exempt from 510(k) premarket notification, subject to the limitations in 21 CFR 862.9.
How the nitroprusside pad works
The reagent in the cleared OTC strip is sodium nitroprusside with a buffer. Ketones (acetoacetic acid) react with nitroprusside and the pad changes color, “ranging from beige for negative results to a dark purple color for positive results.” Results are obtained by direct comparison with color blocks printed on the bottle label; no calculations or laboratory instruments are needed. The strip is packaged with a drying agent in a canister bottle, and technique is either midstream or dip-and-read.
Because the pad is built around acetoacetic acid, the manufacturer wording for these products refers to detecting acetoacetic acid specifically. Ascensia’s KETOSTIX product page, for example, says the strips “detect acetoacetic acid” and that results appear in about 15 seconds.
Types and variants
| Type | Typical use | Key difference | Source |
|---|---|---|---|
| Single-analyte OTC ketone strip (e.g. On Call / Healthy Me, ACON) | Lay users: people with diabetes and low-carbohydrate dieters | Ketone pad only; visually read against bottle color blocks; read time 15 to 120 seconds | FDA 510(k) summary K170587 |
| KETOSTIX (Ascensia) | Urine test for ketone (acetoacetic acid) | Results in about 15 seconds; named as the predicate (K801270) in the FDA summary above | Ascensia product page; FDA K170587 |
| Multi-parameter strip (e.g. Siemens Multistix PRO 10LS) | Professional urinalysis | Ketone is one pad among protein, creatinine, blood, leukocytes, nitrite, glucose, pH and specific gravity; read visually or on CLINITEK analyzers | Siemens Multistix PRO instructions for use, as summarized in our urine test strips guide |
The FDA summary notes that the OTC single-analyte strip is derived from a 10-analyte professional strip from the same manufacturer (K061559), so the ketone pad itself is the same chemistry in both formats.
Specifications that matter
| Specification | Value in the FDA record (K170587) |
|---|---|
| Read time | 15 to 120 seconds for this device; 15 seconds for the Ketostix predicate |
| Ketone levels tested | 5, 15, 40, 80 and 160 mg/dL |
| Urine pH range with no effect on result | 4 to 9 |
| Specific gravity range with no effect on result | 1.000 to 1.040 |
| Light sources tested | Incandescent, fluorescent, sun, mercury and sodium light; results unaffected |
| Interferents | Blood in urine caused false positives (5% blood in testing). No interference from the listed substances tested, including ascorbic acid at 200 mg/dL, glucose and bilirubin |
| Standards referenced | CLSI GP16-A3 and EP7-A2 |
How to choose
- Match the intended use. The cleared OTC strip is for ketone detection and monitoring ketogenic diets; the FDA summary states it is not intended for the management of diabetes.
- Check which pads are on the strip. Multi-parameter strips carry many tests, and the Siemens instructions say to check the label for the tests on the product you use.
- Follow the product’s own read time. Read times in the FDA record range from 15 seconds to 120 seconds depending on the product, so the insert or bottle label for the strip in your hand governs.
- Know the reading method. The OTC strip is read by eye against the bottle label; some professional strips are also read on analyzers such as CLINITEK.
Safe use and handling basics
- Use the sampling technique in the product instructions (midstream or dip-and-read for the cleared OTC strip).
- Compare the pad with the color blocks on that product’s own bottle label, within that product’s read time.
- Keep the strip in its canister; it is packaged with a drying agent.
- Blood in the urine can cause a false positive ketone reading, according to the FDA summary and the product labeling it describes.
- Questions about what a result means for a person’s health belong with a clinician.
Common mistakes
- Reading the color before or long after the stated read time. The window differs by product.
- Using one product’s color chart with another product’s strips.
- Assuming a urine strip manages diabetes. The FDA summary for the OTC strip says it is not intended for that.
- Ignoring blood contamination, which is a documented cause of false positives.
Urine pH strips and the ketone pad (FAQ)
Do urine test strips for pH work the same way as ketone strips?
Both are reagent pads on a plastic strip, but they are different pads. pH appears as a separate test on multi-parameter strips such as Multistix PRO 10LS, which lists ketone (acetoacetic acid) and pH among its pads. A ketone-only strip does not report pH. In the FDA testing for the OTC ketone strip, urine pH from 4 to 9 did not change the ketone result.
What are “ph level urine test strips”?
They are strips (or the pH pad on a multi-parameter strip) used to read urine pH. If you need ketone and pH from one dip, look for a multi-parameter strip and confirm on its label that both pads are present. For broader panels, see our guide to urine test strips.
Are ketone strips a regulated device?
Yes. 21 CFR 862.1435 classifies the ketones test system as Class I and exempt from 510(k). The strip reviewed in K170587 nonetheless has a 510(k) decision summary (product code JIN). For context on how waived tests are handled in clinics, see CLIA-waived test and CLIA-waived point-of-care testing; for the wider clinic supply picture, see the diabetes clinic supply checklist. Buyers can browse diagnostic, monitoring and imaging supplies.
Sources
- FDA 510(k) decision summary K170587, On Call / Healthy Me Ketone Reagent Strips for Urinalysis (ACON Laboratories): accessdata.fda.gov, read 2026-10-29.
- 21 CFR 862.1435, Ketones test system: eCFR, read 2026-10-29.
- Ascensia KETOSTIX reagent strips product page: shop.ascensiadiabetes.com, read 2026-10-29.
- Siemens Healthineers Multistix PRO 10LS instructions for use (Rev A 2017-07), as cited in our urine test strips guide.
