The only supplement every vegan needs to take is vitamin B12. If you have a balanced vegan diet consisting of legumes, grains, vegetables, fruits, nuts and seeds in suitable amounts, you should get all the nutrients you need.

• Iron, calcium and zinc: you can get all these minerals from legumes (especially after soaking or sprouting), whole grains, green vegetables, fortified foods, nuts and seeds. As vitamin C increases iron absorption,
  it's best to add a good source to your meals, such as fresh salad, tomatoes or bell peppers.
• Iodine: you can get iodine from iodized salt and sea vegetables.
• Omega 3: you can get omega 3 (alpha-linolenic acid) from flaxseed, chia seeds, hemp, canola oil and walnuts.
• Vitamin D: our diet has little to do with vitamin D levels, as its main source is endogenic production after exposure to sunlight. In cases of deficiency, a supplement is the best solution. Most supplements contain cholecalciferol – vitamin D3 from an animal source, but you can get vegan supplements based on D2 (ergocalciferol) and D3 from lichen.

It should be noted that in cases of existing deficiency, pregnancy, lactating, infants under one year old or individuals with specific medical conditions which require supplementation (regardless of being vegan), you should consult with a physician or dietitian.