Nutritional supplement to be taken "three times a day": does that mean three different times across the day?

Yes, it means three separate times per day. Ideally with your meals.

I was told by my son’s doctor that if it says “3 times a day” it means basically every 8 hours (4 times a day means every 6 hours, etc. Just evenly space them as best you can manage). If you could take them at the same time it would read “take 3 once daily”

May I ask what the supplement is?

Sounds like it is not a slow release so you have to space it evenly out to maintain the level of release.
But not certain as we don’t know the supplement.
Call the Dr or a pharmacist.

When worded as “three times a day” the common meaning is to take a single dose at each of three different times during the day, roughly 8 hours apart from each other. Generally that means once at the start of the day, once at midday and once before bed.

If the intent were for you to take two doses at any one time, then the instructions would be so worded.

It is best to spread them out to three different times. Also, unless it says otherwise, it is best to take them with food.

Well, just to throw a grenade in all of this, I say it doesn’t matter when you take them because nutritional supplements haven’t been shown to do anything anyway for normal healthy people.

That said there are certainly clinical indications where nutritional supplements are indicated (documented malnutrition for one).

If that is what it says—three TIMES a day—take them at different times. If it says take three daily, you can usually take them at different times or all at once.

This is a supplement that has repeatedly been shown to lessen arthritis pain in good, large, peer-reviewed studies. It’s really not useful to be so dismissive.

@marmoset Definitely take it with food spread out three times per day. Have you tried an anti-inflammatory diet?

With some supplements, there is no storage of surplus. Your body excretes the excess. So yes, as others have said, if it says 3 times a day, you won’t get the same benefits from doubling a morning dose and then taking an evening dose as you would from spreading out 3 doses through the day.