My recipe says 1 unit of lemon juice, what does that mean?
I am not sure if this recipe states that it is American or not but it is for a weight loss, eat healthy program and I do not understand what it is asking me.
It is to show you the ratio of juice to water, but leave the quantity up to you.
This way you can make different amounts: for example 1 unit lemon juice to 3 units water. You could sub in pints or liters or gallons or hogsheads or whatever was appropriate for the amount of lemonade you wanted to make, according to the ratio provided.
The puzzler is how much sugar to add, which is dependent on the amount of fluid. My guess is that there is no sugar as this is a weight loss sort of thing, so really it will just be dilute lemon water.
it is for a weight loss, eat healthy program
These programs usually define their own "units". They try to simplify the calculation of calories, vitamins, and whatever they prescribe to you to eat, by saying that you should eat X units of this and Y units of that per day. The program then also publishes a list of how much of each food makes up one "unit". These definitions are specific to the program, and not shared with other programs or with any other widespread measurements.
So I suggest that you look up the material from that program, to see what their definition of units is.
The internet suggests that another possible meaning of one unit of lemon juice is the juice from one lemon. That is to say, two to four tablespoons of lemon juice.
If you have a bottle of lemon juice rather than a lemon, you can try two tablespoons and add to taste. Or if you have to make it all at once without tasting, try three tablespoons, which seems to be the middle of the range of possibilities. Two tablespoons would also be an eighth of a cup (one fluid ounce), if it's easier to measure that way.
Of course, the recipe might make this clearer. Is this a standalone amount (e.g. one lemon) or a ratio (e.g. one part lemon to four parts water)? Or something else?
For example, in this recipe, it is probably one lemon. I would also guess a glass is one cup of water, but it's not exactly clear on that either.
1 unit Lemon juice
1 tablespoon Chia seeds
1 tablespoon Honey
1 ½ glasses Water