The absolute best way to avoid nutritional deficiencies is to feed the feeders a nutritious diet, supplement on a recommended schedule (see Resources tab for species caresheets with supplement info) and to make sure that your chameleon has all that he physically and psychologically needs.
Nutritious feeders are made that way by feeding them fresh fruits and vegetables, grains, etc.
The majority of commercial gutloads/insect diets tends to be inferior.
Don't overlook the importance of proper temperatures for your chameleon.
Temps too low can lead to nutritional deficiencies and other health problems, such as low immune system function.
Your cham needs to be at a certain temperature in order to utilize the vitamins and minerals that food provides, since his body can't make its own heat.
(Temps too high also cause serious health issues or death.)
As good as vitamin and mineral supplements are, you don't want to overdo them.
Too much is at least as bad as too little is.
Here's the Veiled chameleon caresheet for you
https://www.chameleonforums.com/care/caresheets/veiled/
I saw another post of yours where you mention owning bearded dragons (my favorite tough as nails kind of lizard).
Please be sure to always wash your hands after handling beardies before handling your cham or his enclosure.
Don't underestimate the importance of meeting chams' psychological needs .
It is very important to ensure that your chams can't
see the beardies (or each other) from their enclosure.
Beardies are predators, chams are prey.
Being able to see that they're near the beardies will stress your chams.
Being able to see each other stresses chams, too, as they are very territorial, with the exception of a few types of chams.
I recall a few years back when a fellow chamkeeper couldn't figure out why his cham had stopped eating.
He posted pics of the cham setup and it was noted that the cham enclosure was next to his beardie's enclosure.
After relocating his cham away from the beardie, the cham resumed eating.
A visual barrier works just as well, if they need to be located in the same room.
Glad to see a new cham owner asking questions.
Especially when it comes to chams, an ounce of prevention is definitely worth a pound of cure.