Please check this sentence, gramatically

Can a person who drinks a low amount of liquids have higher blood density than a person who drinks an even lower amount?

Ok, excuse me I took mistake. I wanted to say:
Can a person who drinks low liquids have higher blood density than a person who drinks more?
2- Why should we use "a low amount" ? Why cannot we just use "low amount"?

Alex John Can a person who drinks low liquids have higher blood density than a person who drinks less?

What do you mean by the "low liquids"?
The question should be formulated like that:

Can a person who drinks liquids of higher density have higher blood density than than a person who drinks liquids of lower density?

The answer is "Yes".

Why should we use "a low amount" ? Why cannot we just use "low amount"?
Amount is a countable noun, so it needs a determiner, eg an article.

That's why we say eg 'a red chair' instead of just 'red chair'.

So what about "An increase in demand" or "Increase in demand"

I checked it in Longman dictionary. AMOUNT is countable and uncountable. So we can use LOW AMOUNT.

Do they give an example of an uncountable use of 'amount'?

You can't say 'He drinks low amount'.

Yes, I got it. It's given a template as "a small, tiny ,etc. amount of sth"