When we say someone or something is "low on" something, it means they are lacking it. There are various synonyms that can be used to express this situation, such as scarce, depleted, deficient, inadequate, short, or meager. All these words imply a shortage or insufficiency of something that is vital or necessary, such as money, food, resources, energy, or motivation. Being "low on" something can result in difficulties or hardships, especially if it is something crucial, such as being "low on" water in a desert or "low on" time before a deadline. Therefore, it is important to keep an eye on what we lack or need to avoid getting "low on" it.