Dietary supplements are concentrated sources of vitamins, minerals, botanicals or other bioactive ingredients sold in dose forms like tablets and capsules to complement the diet. Quality concerns include accurate dosage, purity from contaminants such as heavy metals, and truthful labelling, since regulation is lighter than for medicines in many countries. Consumers should treat bold health claims skeptically and recognize that supplements cannot compensate for a poor diet. Third-party certification marks offer some assurance of quality. Health professionals advise obtaining nutrients from food first, using supplements only to fill specific, identified gaps.