Exogenous ketones / ketone esters

What it is

The liver forms ketone bodies when few carbohydrates are available, for example during fasting. The most important one is beta-hydroxybutyrate, BHB for short. The heart and brain can use it as fuel. Exogenous ketones supply BHB from outside, without having to change your diet.

There are two main forms. Ketone salts bind BHB to sodium, potassium, magnesium or calcium. Ketone esters, usually (R)-3-hydroxybutyl (R)-3-hydroxybutyrate, are completely broken down in the body; the intact ester cannot be detected in the blood, but BHB and acetoacetate rise. In a direct comparison, the ester reached a peak of 2.8 mM D-BHB, the salts only 1.0 mM. The salts also consisted half of L-BHB, a form that cleared much more slowly and stayed in the blood for more than 8 hours.

After a ketone drink, the level rises within minutes and falls again after 3 to 4 hours. With a meal beforehand, the peak was 33 percent lower. All drinks also lowered blood glucose, free fatty acids and triglycerides.

How it is supposed to work

The basic idea is an additional fuel that is available independently of sugar. In sport this was supposed to extend endurance; in aging and Alzheimer’s it was supposed to better supply a brain with impaired energy metabolism.

In addition, BHB acts as a signaling molecule. In 15 healthy people, a ketone ester lowered the hunger hormone ghrelin, and hunger and desire to eat were lower 1.5 hours later than after a sugar drink with the same calories. In the heart, ketones apparently increase cardiac output and lower vascular resistance, as short studies in heart failure show.

What users are looking for

Most people reach for ketone drinks for a clear head in the morning, as a bridge into ketosis at the start of a ketogenic diet, or as energy in endurance sport. The studies best support the first two uses. For sport, the balance is more sobering than the advertising promises.

What the studies show

Ketones and performance, meta-analysis 2020

The analysis included 13 randomized trials in which ketones were taken shortly before exercise, from sprints to about 50 minutes of endurance. No effect on performance was found, neither with esters nor with salts (Hedges g -0.05). Lactate, heart rate and perceived exertion did not change consistently either. A second meta-analysis from 2022 with 8 studies and 80 participants reached the same result.

Ketones and cognition, meta-analysis 2026

Randomized, placebo-controlled trials with healthy people and people with neuropsychiatric conditions were included. 29 protocols with 1,117 participants entered the calculation. The result was a small benefit (SMD 0.29), regardless of whether esters, salts or other forms were used. The authors see a need for larger and longer studies.

28 days of ketone ester, 2019

24 healthy adults aged 18 to 70 drank a ketone monoester three times a day for 28 days. The BHB level rose each time from 0.1 to 4.1 mM. Weight, body composition, blood glucose, blood lipids, electrolytes, blood gases and kidney values remained unchanged. There was no placebo group; the study is still the longest safety study of its kind.

Ketones in heart failure, 2026

The meta-analysis pooled 4 randomized trials with a total of 94 patients. Cardiac output and ejection fraction rose, vascular resistance fell, and heart rate rose by 4.08 beats. The studies were short and mostly of crossover design; the authors draw no firm clinical conclusions.

Ketone drink and hunger, 2018

15 normal-weight adults drank, after fasting, either a ketone ester or a sugar drink with the same calories, matched in volume, taste and color. After the ketone drink, BHB rose from 0.2 to 3.3 mM within 60 minutes. Two to four hours later, insulin and the hunger hormone ghrelin were lower, as were hunger and desire to eat after 1.5 hours. Only a single morning was measured; whether people eat less in the long term as a result is open.

Where the data stop

The biggest gap between advertising and data lies in sport. Two meta-analyses found no performance benefit; a newer review of 26 studies describes an inconsistent picture with isolated improvements, no benefit or even worse performance. The acidification caused by ketone esters appears to play a role here; together with sodium bicarbonate it was smaller.

For cognition and the heart, the effects are small and based on short studies with surrogate markers such as test results or cardiac output, not on the course of dementia, hospital admissions or survival. A systematic review of 51 studies in disease reaches the same conclusion: many indications, hardly any hard endpoints. Whether ketone drinks are safe in the long term is open, because the longest safety study ran for 28 days.

Status, approval and legal

Ketone salts made from sodium, magnesium and calcium BHB are a non-authorized novel food in the EU. In 2022, EFSA reviewed an application and found that the information on identity, production and composition was insufficient; a safe intake level could not be set. For the ketone ester, there was no entry and no authorization in the European Commission’s Novel Food Catalogue. There are no medicines with exogenous ketones, and no authorized health claims either. Ketones are not on the 2026 WADA Prohibited List. Because these are not approved active substances, Biohacking Kompakt does not state a dosage.

Safety

Mainly gastrointestinal complaints have been described, especially with large amounts. Ketone esters slightly acidify the blood; in one study, the pH fell by 0.10. Ketone salts, by contrast, deliver a lot of sodium or potassium and made the urine considerably more alkaline, which should be considered in high blood pressure or kidney disease. Because ketones lower blood glucose, people on diabetes medication should take them only after consulting a physician. EFSA could not confirm the safety of the salts, partly because of unclear product quality. There is no upper limit from EFSA, BfR or NIH; data are lacking for pregnancy, breastfeeding and children.

Sources

• Stubbs et al., Front Physiol 2017
• Valenzuela et al., Int J Sports Physiol Perform 2020
• Brooks et al., Int J Sport Nutr Exerc Metab 2022
• Bonnechère et al., Front Nutr 2026
• Soto-Mota et al., Regul Toxicol Pharmacol 2019
• Stubbs et al., Obesity 2018
• Siddiqi et al., World J Crit Care Med 2026
• Martí-Martí et al., Life 2026
• EFSA NDA Panel, BHB salts as a novel food, EFSA Journal 2022