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There are three important ketones involved in [[Ketogenic Diet]]s.
* '''Acetoacetic acid (AcAc)'''. AcAc is the ketone that is produced by the liver from fats and can be metabolized to provide energy. It could be considered the most directly useful of these ketones to the human body. However, AcAc lowers the blood pH, causing potential acidosis. AcAC spontaneously decomposes into Acetone (half-life 11.7 hours at 27c<ref name="HayBond1967"/>).
* '''Acetone'''. Generally is often believed to be a waste product, but it has now shown to be metabolically active. It is excreted through the breath and urine, which can sometimes be detected as a fruity smell.
* '''Beta-hydroxybutyrate (BOHB)'''. Unlike AcAc, BOHB is stable and does not change blood pH. AcAc is converted to and from BOHB in the liver and muscles. Technically BOHB is not a Ketone.
=Relative Ketone Levels=
* The ratio between AcAc and Acetone appears reasonably constant, and is based on the spontaneous, one way decomposition of AcAc into Acetone.
* The ratio of AcAc to BOHB is rather more varied and may change with [[Ketoadaptation]].
From "Physiological roles of ketone bodies as substrates and signals in mammalian tissues"<ref name="Robinson-1980"/>:
{| class="wikitable"
! Situation
! Ketone Levels (Blood levels of AcAc + BOHB)
|-
| Fed
| ~0.1
|-
| Fasted 12-24 Hours
| Up to 0.3
|-
| Fasted 48-72 Hours
| 2-3
|-
| Fasted 5-6 weeks (plateau)
| ~8
|-
| Post exercise
| Up to 2
|-
| Late Pregnancy
| Up to 1
|-
| Late Pregnancy, fasted 48 hours
| 4-6
|-
| Neonatal
| 0.5-1.0
|-
| Hypoglycemia
| 1-5
|-
| Controlled diabetes
| Up to 25
|}
=Ketone Metabolism=
=References=
<references>
</references>