Should I consult a doctor before taking these or is it not necessary to do so since it is a herbal product?
"Herbal" products contain active ingredients that affect cells in your body, just like manufactured products (i.e. "medications"). If the ingredients did not affect your body's cells, then how could they provide benefit? If your herbal product works (i.e. achieves the aim for which you bought it, i.e. weight loss, pain relief, so on), then you can bet that there are side effects that may be experienced by some people, and allergies experienced by some people, and interactions with other products/medications.
It's a myth that because these products are "natural", they cannot hurt you. Bacteria is "natural". Viruses are "natural". Cancer is "natural".
I'm not saying these products are bad. In fact, a lot of them do good for a lot of people. I'm just saying you should treat them with the respect they deserve - and if you expect them to treat you like a medication, you should realise that they can have risks like any other medication.
So you should ALWAYS see your doctor before starting any herbal tablets/supplements, because it is possible that they can interfere with other medications that you take! Or may not be appropriate for your particular condition..
Summary: Just because a product is bought over the counter, it does not make it 100% safe. Nothing is 100% safe. Panadol can kill people, if used incorrectly.