Do you eat low-carb, fast regularly or train for a long run? Then you may wonder what is actually happening in your body. With a drop of blood from your fingertip, you can measure your ketone level yourself at home, with no appointment and no waiting room. This guide explains what ketones are, when measuring makes sense, how the measurement works and how to read your values. All information is based on the manufacturer's instructions for use and on scientific literature. You will find the sources at the end of the article.
What are ketones?
Normally the body covers a large part of its energy needs with carbohydrates. When fewer carbohydrates are available, for example during fasting or on a low-carbohydrate diet, the liver produces more so-called ketone bodies. They then serve as an additional source of energy [2].
There are three ketone bodies: acetoacetate, acetone and β-hydroxybutyrate (β-OHB). β-hydroxybutyrate is considered the main ketone body in the blood [3]. This is exactly the value the FORA 6 Connect measures with the ketone test strip [1].
When do ketone levels rise?
Without fasting and on a normal diet, the β-OHB level in the blood is very low. In a laboratory study, the reference range of healthy people was about 0.02 to 0.28 mmol/L [3].
The level can rise:
- during fasting [1, 2]
- on a low-carbohydrate or ketogenic diet [2]
- after strenuous physical exercise [1]. A study with runners also showed that the rise after training depends strongly on how many carbohydrates were eaten in the days before: more carbohydrates dampened the rise, fewer carbohydrates increased it [4].
In the scientific literature, nutritional ketosis is defined as a blood β-OHB level of 0.5 mmol/L or more [2].
When does measuring make sense?
- Low-carb and ketogenic diet: you see how your diet affects your ketone level.
- Intermittent fasting: you compare your values on fasting days and normal days.
- Endurance sport: you observe how your level changes after long or intense sessions.
The trend matters more than a single value. So measure under similar conditions, for example always at the same time of day and at a similar interval after your last meal or training. That way your values are easy to compare.
Why measure in the blood?
Ketones can be measured in blood or in urine. The two methods do not measure the same thing:
- Urine test strips react to acetoacetate, not to β-hydroxybutyrate. The urine value also depends on kidney function, fluid intake and medication. One study therefore describes it as only a rough and time-delayed estimate [3].
- Blood measurement detects β-hydroxybutyrate directly. According to the same study, this value corresponds directly to the current state of ketosis [3].
How to measure with the FORA 6 Connect
- Once per new pack: set up the meter. Insert the code strip supplied into the switched-off meter and wait until the code number appears. Remove the code strip. The meter is now set up for this pack [1].
- Wash your hands and dry them well.
- Insert the ketone test strip. The meter switches on automatically. Check that the code shown matches the pack [1].
- Prick your fingertip. For ketone measurement, only blood from the fingertip is intended, not from the palm or the arm [1].
- Apply the blood. The strip needs at least 0.8 µL of blood. After 10 seconds you see your result [1].
- Eject and dispose of the strip. The eject button releases the strip without touching it. Dispose of used test strips and lancets according to local regulations.
The measuring range is 0.1 to 8.0 mmol/L. If the meter shows "Lo", the value is below 0.1 mmol/L: repeat the measurement with a new test strip. "Hi" means a value above 8.0 mmol/L [1].
The meter stores your values with date and time. Via Bluetooth you transfer them to the iFORA app and keep track of your trend over weeks.
Tip: how to get a clean blood sample and avoid measuring errors is explained in our guide Measuring blood glucose correctly: 8 tips for accurate results. The tips also apply to ketone testing.
Understanding your values
| Blood β-OHB | Meaning | Source |
|---|---|---|
| approx. 0.02–0.28 mmol/L | reference range of healthy people in a laboratory study | [3] |
| below 0.6 mmol/L | normal range according to the manufacturer | [1] |
| from 0.5 mmol/L | described as nutritional ketosis in the scientific literature | [2] |
For people with diabetes, the manufacturer also states [1]:
- 0.6 to 1.5 mmol/L: this may indicate a developing problem. Follow your doctor's instructions.
- Above 1.5 mmol/L: contact your doctor promptly. There may be a risk of diabetic ketoacidosis.
For context: nutritional ketosis is not the same as ketoacidosis. In ketoacidosis, levels are much higher; the literature often cites a cut-off of 3.0 mmol/L. In patients with diabetic ketoacidosis, one study measured levels of about 3 to more than 10 mmol/L [3].
Which range suits your diet or training is best discussed with your doctor or a nutrition professional.
When should you seek medical advice?
- If you have diabetes and your level is above 1.5 mmol/L: promptly [1].
- If a result does not match how you feel [1].
- Before changing any medication because of a measured value [1].
Self-testing does not replace a medical diagnosis. It helps you get to know your values and discuss them at your next doctor's appointment.
Frequently asked questions
Do I need a separate meter for ketones?
No. With the matching test strip, the FORA 6 Connect also measures blood glucose, total cholesterol and uric acid.
Do I have to set up the meter every time?
No, only once per new pack of ketone test strips, with the code strip supplied [1].
Can I also measure on my arm or palm?
No. For ketone measurement, only blood from the fingertip is intended [1].
How often should I measure?
That depends on your goal. More important than frequency is measuring under similar conditions, so that your values are comparable.
How do I store the test strips?
In the original packaging, dry, at 2 to 30 °C and not frozen. Do not use expired test strips. The expiry date is printed on the pack.
How are the test strips packed?
In bags of 10, each strip individually wrapped.
Start measuring now
- Already have a FORA 6 Connect? → Ketone test strips for FORA 6
- Want to get started? → FORA 6 Connect with 10 ketone test strips
- Everything about measuring ketones: Measuring ketones
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Sources
[1] ForaCare: FORA 6 Connect Owner's Manual, version 2.0, 2018, document no. 311-4183400-025. Sections on β-ketone testing.
[2] Saris CGJ, Timmers S. Ketogenic diets and ketone suplementation: A strategy for therapeutic intervention. Frontiers in Nutrition. 2022;9:947567. https://doi.org/10.3389/fnut.2022.947567
[3] Kraus FB, Kocijancic M, Kluttig A, Ludwig-Kraus B. Test validation, method comparison and reference range for the measurement of β-hydroxybutyrate in peripheral blood samples. Biochemia Medica. 2020;30(1):010707. https://doi.org/10.11613/BM.2020.010707
[4] Koeslag JH, Noakes TD, Sloan AW. Post-exercise ketosis. The Journal of Physiology. 1980;301:79–90. https://pubmed.ncbi.nlm.nih.gov/6997456/
