Ketosis is an elevated presence of ketones in your blood. It is usually measured indirectly, by detecting ketonuria - the presence of ketones in your urine. Home testing kits, such as Ketostix, can be purchased at your local drug store in the diabetics section. For the purposes of LC, trace indications are sufficient - it is not necessary to show "strong" ketosis, and may be suboptimal in the long run.

Note that it is possible to be in ketosis without also being in ketonuria. This is common after the first month of LC, when your body adapts and doesn't overproduce ketones as much.

It is also possible to detect ketosis indirectly by being aware of its side effects, such as hunger reduction or water loss (diuresis). Some folks notice "ketobreath" although others claim that's from excess dietary protein. Note that color and odor of urine is normally caused by other factors, not ketones.

If you weigh yourself every day, you may notice that carb consumption results in sudden weight changes due to water retention in conjunction with glycogen storage. The liver stores about 100g of glycogen, for a total of about a pound of weight with water, and your muscles store more. You could use these sudden weight changes as indicators of glycogen storage (or at least for CCLL discovery), which is one factor influencing ketosis, if you have no other way of detecting ketosis.

The net result is, if you're losing weight and you're not hungry, you're doing it right :-)