Insider discusses what women should know about vitamin supplements and instances when it is necessary to take them according to Rebecca Tonnessen, RDN, nutritionist at HSS.

"There are two ways to know if you need to take supplements: Your doctor can test the levels in your blood, or you can evaluate your diet and supplement the nutrients that you are unable to obtain through your foods. For example, if you are following a special diet, such as a vegan diet, you may consider talking to a professional about the appropriate supplements to take," said Tonnessen. Certain symptoms can also indicate nutritional deficiencies. "Signs that your nutrition may be sub-optimal include brittle nails, dry skin, and bleeding gums," she continued.

Tonnessen counseled on which supplements to take by age, and that while vitamin and mineral supplements can help meet nutrition requirements, they should be taken cautiously. "Always try to increase your food intake of vitamins and minerals before relying on supplementation. Consult a healthcare professional prior to starting a supplement as some nutrients, such as iron, can be dangerous if taken in excessive amounts. More is not always better," advised Tonnessen.

Read the full article at Insider.com.