I use them myself... kids have extra vit C for immune system, probiotics for my ds when he will take them... b12, and and fish oil.

We are using a couple of supplements right now with success,but you may want to speak to your peditrician before you begin.
We have had luck with probiotics, DHA, DMG,and b12

Any supplementation isn't necessarily to treat autism, but address some of the common co-morbidity and nutritional deficiencies commonly found in ASD. Here is a good research paper on this on the nutrition and metabolic findings though cannot say the same for a specific child (which is why testing is important).

http://www.nutritionandmetabolism.com/content/p...

Even for our NT son, we give a multi, zinc, iron, omega-3 and vitamin C (and infrequently B-vitamins since he doesn't eat much vegetables).

However, for our ASD son, in addition to above common supplements, we have specific supplementations based on research and testing with the two most important ones being MB12 and methyl folate - that was a wow for us. Our core focus has been to improve methylation and reduce oxidative stress.

A change in diet can have even more profound changes for some (specifically removing casein) rather than supplementation, so that would be where I would start if considering this.

The biggest gains we have seen have come literally within days of starting certain supplements. Traditional therapies are important, too, but those gains have been of the "slow and steady" kind, rather than the dramatic ones we have seen with biomed. Specifically DD has responded positively to acetyl-L-carnitine, Coenzyme Q10, Behavior Balance DMG, and the methyl B12 injections. All of those except the mB12 are available without a doctor's prescription. I also give Klaire Labs VitaSpectrum multi and Coromega fish oil but those don't seem to make a difference one way or the other. I have given probiotics from time to time in the past but they don't seem to make a difference for my DD.

In general, agree with your pediatrician that the "standard" blood tests are usually not accurate as it shows what is available in the serum only, but not what gets into cells where it is needed, and whether it is being used properly. There are two simple tests that one can do - hair test and Organic Acid Test. While neither are 100% accurate, there are not invasive and it gives you an idea what maybe off and should be tested further with more accurate tests.