Exogenous Beta-Hydroxybutyrate (Ketone Supplements): From Bench to Bedside Trials

Beta-hydroxybutyrate (BHB) is the dominant ketone body produced during fasting, prolonged exercise, and the ketogenic diet. Exogenous ketone supplements — ketone salts (sodium, potassium, calcium, or magnesium BHB) and ketone monoesters (R-3-hydroxybutyl R-3-hydroxybutyrate) — raise blood BHB without requiring caloric restriction. The supplement category has gone in four years from "metabolic curiosity" to a serious clinical trial pipeline in heart failure, neurodegenerative disease, and acute brain injury.

What raises BHB and by how much

Ketone monoesters (KME) raise blood BHB to 2–6 mmol/L within 30–60 minutes after a 25 g dose. Ketone salts produce smaller peaks (0.5–1.5 mmol/L) because dose is limited by the cation burden — eating 25 g of sodium BHB delivers about 3 g of sodium, which is not sustainable. The monoester is the form used in most modern clinical trials; it is unpleasant-tasting but reliably effective at raising BHB [1].

Heart failure — the most advanced indication

The failing heart shifts its substrate use away from fatty acid oxidation toward ketone bodies; ketone uptake is increased in heart failure with reduced ejection fraction. A series of acute infusion and oral trials have shown that raising BHB to 3–5 mmol/L increases cardiac output by 8–15%, improves stroke volume, and reduces systemic vascular resistance in patients with HFrEF [2]. Longer-term oral trials have shown improved exercise capacity and quality of life over 4–8 weeks. A larger phase III trial of KME in HFrEF is now ongoing.

Neurodegenerative disease

The brain readily takes up BHB as fuel when cerebral glucose metabolism is impaired — as it is in Alzheimer's disease. Small trials of KME in mild cognitive impairment and early Alzheimer's have shown improved memory and executive function scores during acute BHB elevation [3]. The mechanism — bypassing impaired glycolysis to fuel mitochondria — is biologically attractive but the clinical effect sizes are modest and durability is unclear. A 6-month trial in early Alzheimer's is in progress.

Athletic performance

The early hype around ketone supplements in endurance athletes has not been borne out. Most controlled trials show no improvement in time trial performance with KME, and some show slight decrements due to acidosis at high doses [4]. There is a possible benefit in recovery (improved glycogen replenishment when combined with carbohydrate) but it is small. Ketone esters are not a competitive ergogenic in any reliable sense.

What about safety

BHB elevation to 1–6 mmol/L is well tolerated short-term. The main acute issue is GI distress (nausea, vomiting, diarrhea), which is dose-limiting for most users. Mild metabolic acidosis occurs with ketone salts; ketone esters acidify less. There are no documented serious adverse events in trials up to 3 months. Long-term safety beyond 6 months has not been established [5].

The big unknown

It is not yet clear whether raising BHB acutely provides clinical benefit only during the elevation, or whether sustained or repeated dosing produces durable adaptation in mitochondrial function, gene expression, and cardiac substrate handling. The animal literature suggests durable adaptation; the human literature is too short to tell. This is the question that the ongoing 6-month heart failure and Alzheimer's trials will answer.

Where this stands in 2026

Ketone monoesters are in serious clinical development for heart failure and neurodegenerative disease, with phase II data supporting biological effect. For consumer use, the products are expensive ($5–15 per dose), the taste is unpleasant, and the demonstrated clinical effects in healthy people are modest. Athletes who have tried them and stayed with them are unusual. People interested in ketone supplementation for neurodegenerative or cardiovascular disease should look for ongoing trial enrolment rather than buying products empirically; the dose, formulation, and patient selection matter substantially.