Your doctor can't say because this is an herbal supplement, the documentation of which has been questionable as to whether it does purify the liver or aid in any way.

There are many ways to look at herbs and whether they are beneficial or no better than a placebo.
Herbalism is divided between people believing some plants are magic, people that believe that they provide you with an energy field that will flow through you, and people that believe the basic chemical components that make up the herb are what are useful as medicine. The latter is, to me, the realistic approach.

Most modern herbologists concede that pharmaceuticals are more effective. Therefore if you want to take a supplement, take one your doctor recommends. He's been studying medicine for quite some time, and is there to help you.

If you're looking to supplement your pill regiment, then milk thistle should not be directly damaging since it doesn't contribute any iron to your body, but unless this is necessary I wouldn't risk trying an herbal supplement as the sole means of getting better (pharmaceuticals would be safe as the sole means of getting better)

no ..milk thistle is one of the few very researched herbs. It is also one of the most effective for helping the liver. It works by both protecting the liver from toxins (it has been used in hospitals to prevent liver damage from snake and spider bites) as well as increasing the speed at which liver cells regenerate. Milk thistle is also invaluable if you drink alcohol frequently. It is very safe to use. and the dossage given on the bottle is for general use, if you are using this to treat an already damaged liver you will need to increase the dose by a factor of 2 or three. I would seriously consider finding a doctor who is up to date with things other than just pharmaceuticals, most pharmacists actually are schooled better than doctors in contraindications between herbs, so you can swing by any cvs or other pharmacy and ask the pharmacist specific questions. There is a clinical book put out that all doctors are supposed to be familiar with, sounds like your doctor needs to get up to speed.