Along with providing mineral rich, quality foods, it may also be a very good idea to supplement the diet with additional vitamins and supplements. No matter how well you plan a diet for your iguana, there still may be a chance of vitamin deficiencies. While supplementing is a good idea, over supplementing certain vitamins can be very dangerous. Before deciding to supplement your iguana's diet, it's a very good idea to ask your vet about the necessary needs of vitamins and supplements. Please visit our Veterinarians & Societies page for more information on how to find a qualified vet. It's still unsure as to whether or not vitamin supplements are necessary. Some experienced iguana owners claim that it is a necessary part of feeding, while others claim that it is not needed if a high quality diet of mineral rich foods is provided. The Green Iguana Society would like to state that although there are many people on both sides of this debate, we still feel vitamins and supplements, if used properly, can be a good practice and that it's important to always use extreme caution when supplementing.
Commercial reptile vitamins - There are many different brands of vitamin supplements available, but many of the more popular varieties are inadequate or unsafe for your iguana. Many contain added phosphorus and D3. It's still unsure whether or not iguanas need additional dietary vitamin D3, and too much vitamin D3 may lead to serious health problems. Rep-Cal Herptivite is an all natural vitamin supplement. It was the first herp supplement to be made with only beta carotene and not vitamin A, therefore preventing vitamin A toxicity. It's also made with a natural sea vegetation base instead of with artificial fillers. HerpCare Calcium Supplement is a powdered calcium supplement that contains only Calcium Carbonate, without D3 or phosphorus. Rep-Cal Calcium (without D3) is another excellent calcium supplement, as long as you buy it without D3. Those are the only vitamin supplements made specifically for reptiles that we recommend.
Other ways to supplement - Most experienced iguana owners who supplement their iguana's diet prefer to use other types of vitamins, rather than buying the usually more expensive commercial reptile varieties. A good way of doing this is buying human vitamins and supplements, easily found in most pharmacies. If the supplements you buy are in tablet form, you'll need to crush them into a powder, and you may consider buying a mortar and pestle (as shown in the first photo below) to make crushing the tablets much easier. Also, some containers to put the crushed powder in makes adding the supplements a very simple chore. Shakers (as shown in the second photo below) used for cooking (for example, sugar containers, large salt and pepper shakers, grated cheese shakers, etc.) are ideal and can be found in most stores such as Walmart. Be sure to use the shakers just for the iguana's supplements and make absolutely sure they won't be mistaken for human use. Clearly labeling the containers as "Iguana Vitamins" will prevent any accidents.
Calcium supplements - The best way to provide extra calcium is by using Calcium Carbonate. It can be found in tablet or powder form in most pharmacies. If you can't find it, you may have to ask the pharmacist for it. Another popular source for calcium supplementation is using crushed Tums tablets which can be purchased almost anywhere.
Multi-vitamins - Many iguana owners supplement their iguana's diet with human multi-vitamins such as Centrum or a generic equivalent. These are in tablet form, so you will have to crush them into a powder before you use them. Multi-vitamins made specifically for women can be a good choice as well because of the higher calcium content than regular multi-vitamins.
Protein supplements - Since some vegetables don't contain a great deal of protein, it can be a very good idea to boost the protein in your iguana's diet. This can be done with adding shredded mature alfalfa or high quality rabbit food to the food, but the best way is with crushed alfalfa tablets (as shown on the left in the photo above) that can be found in most pharmacies. Crushed alfalfa tablets should be added to the food just before feeding and not stored with the food.
How to, how much, how often - Since it is still unsure as to exactly how much of what vitamins are needed, finding the correct dosage of vitamin supplements can be a difficult thing to determine. Most problems occur due to lack of vitamins and problems with over supplementing is rarely seen in iguanas. Vitamin supplements can be added after you prepare the food or just before serving. If you're using shakers to apply the powder, then it's recommended that you apply it just before serving. Juvenile iguanas have a faster growth rate, so most believe they should be given more. It is usually recommended that juveniles be given a small pinch of vitamins or a light dusting about every other feeding and adults once or twice a week. The pinch should be a small one and it's not necessary to coat the entire meal with the vitamin powder. It's also a very good idea to provide extra calcium for gravid females.
Supplements for frozen food - If you are feeding your iguana food that has been frozen, it's recommended that you supplement it with crushed thiamin (vitamin B1) tablets or brewer's yeast. Freezing can break down the thiamin (vitamin B1) so frozen food should be always be supplemented with a very light sprinkling before feeding which should be enough to replace the lost thiamin.
Supplements by Melissa Kaplan gives some great "middle-of-the-road" advice
on what kind of vitamin supplements are best as well as recommendations on how much to give