How to Help Your Iguana Gain Weight
Green iguanas are one of the most popular pet lizards in the United States due to their high availability and cheap initial price tag. Iguanas can do very well in captivity and many of them can thrive for 25+ years with the proper care (or sometimes, even not so great care), however, there's still an unfortunately high number of iguanas that are purchased and given the wrong husbandry. Improper husbandry, illness, stress, and other conditions in captivity can lead to weight loss.
If your iguana seems too skinny, is underweight, or is refusing to eat, you’ll want to ensure that you are providing it foods that will help it efficiently gain weight.
Baby and juvenile iguanas often look skinnier than adults.
It is especially problematic if your iguana is showing signs of depression, listlessness, inactivity, and closing its eyes for long periods only to open them in your presence. This iguana has a high chance of not recovering without medical intervention.
If your underweight iguana is otherwise bright, alert, and reasonably active, you can attempt to see if a dietary change can be helpful in restoring it to a healthy body condition.
If Your Iguana Isn’t Eating
A common problem with green iguanas that can lead to weight loss is anorexia, or refusal to eat, and this can be caused by a few conditions:
- If the iguana is a sexually mature female and is only losing weight in its legs (not the torso), she could be gravid, and it is normal for their appetite to be reduced.
- Your iguana is stressed by a recent move, another animal or iguana, lack of security, ect.
- The iguana is sick
If you have a skinny iguana, it is important to find out how it got that way first. While iguana forums can offer some insight, that is a poor substitute for taking the iguana to the vet for the appropriate tests (x-rays, CBC blood count, parasite test) to find out why it is losing weight.
Sometimes iguanas that are severely dehydrated can appear to be ‘skinny’, and it is important to distinguish the two because they require different treatment approaches. If you suspect that your iguana is dehydrated, it is best to get the iguana evaluated by a vet, particularly if the signs are severe and the iguana has a behavioral change. The following signs may indicate dehydration 
- Sunken eyes
- Thickness and durability of skin tent or folds
- Saliva forms 'durable' strands
- 'Doughines' to the abdomen
- Rapid weight loss in less than a few weeks
To hydrate a moderately dehydrated iguana or while waiting for veterinary care:
- Soak the iguana in a warm bath for at least 15 minutes, making sure that it is strong enough to raise its head to avoid drowning. Soaking is not a replacement for drinking; some sources claim that iguanas can 'drink' through their cloaca, although there is no evidence of this .
- Only attempt to feed iguanas that are not severely dehydrated and are bright and alert, otherwise regurgitation or aspiration can occur . Offer regular food with extra water sprayed on.
- Add more moist foods and fruits like cucumber, watermelon, and zucchini .
- If the iguana is eating, put its food in some water to 'train' it to drink more .
- Run a humidifier for at least 12 hours a day, aiming for 60% humidity in the enclosure, or spray the iguana and enclosure with a light mist several times per day .
- Some iguana owners recommend administering a little Pedialyte, or you can try this homemade slurry designed by the Iguana Den.
Healthy Diet and Proper Husbandry
In most cases, the safest way to help an iguana gain weight is simply to provide it with a properly balanced, nutritious diet. As long as your iguana is not critically ill, they should be able to gradually put on weight in a healthy manner, which is the safest way.
In addition to the right diet, it is essential that all aspects of the iguana’s husbandry are adequate, or your iguana may not be able to benefit from the right nutrients . Besides nutrition, the most common errors that iguana owners often make that can prevent them from staying healthy are improper temperature, lighting, and humidity.
Quick Tips for a Healthy Iguana
- Provide your iguana with UVB/UVA rays with the right lighting placed at the correct distance, as well as unfiltered (no glass) natural sunlight as much as possible.
- Your ambient temperatures should range from 82-87 degrees during the day with a basking spot of 95-120 degrees .
- Let your iguana soak for 15 minutes at least a couple times per week.
- Most owners recommend feeding mostly high calcium leafy greens.
- Keep researching your iguana’s needs from multiple sources.
Good Websites to Start
- Melissa Kaplan's Green Iguana Care Collection
Extensive information on the captive care and behavior of green iguanas, and other reptiles and amphibians, by Melissa Kaplan, author of Iguanas for Dummies.
- The Green Iguana-Captive Care by Petra Spiess
- Feeding Iguanas
The Green Iguana Society is dedicated to providing quality information on iguana care as well as information on current adoptions and rescues throughout the United States & Canada.
While this book, considered by many to be the iguana 'bible', is older, its information still remains true today. I've been using the information in this book with my iguana for over 15 years.
A ‘normal’ iguana diet that will help a thin iguana with no ailments reach a healthy weight should include 40%-50% ‘staple’ greens, 30%-40 ‘other' vegetable's, and the rest of the diet can be composed of different foods such as fruit, grains, legumes and beans (more protein from foods such as legumes for baby iguanas) . It is recommended that growing baby iguanas receive over 22% protein, with 27% being preferred .
Iguanas in the wild are mainly folivorous and while they may consume occasional insects and carrion, particular when they are growing babies  it is generally recommended to avoid feeding animal protein to captive iguanas .
Ideally there should be 5 different types of plant material per salad. A more thorough list of the foods that are considered staples are listed in the Green Iguana Food Information Chart.
Foods for Weight Gain
After you have addressed the underlying cause of your iguana’s weight loss you can add foods that are higher in protein and calories.
For sick iguanas and those that are not eating well on their own, Critical Care is the food of choice by many owners and veterinarians. It can be ordered on Amazon or purchased more quickly at most veterinarian practices that see exotic pets.
The most popular variety is Apple Banana but there is also Fine Grind. This food needs to be mixed with water (or for dehydrated iguanas, pedialyte can temporarily be used) until a good consistency for syringe feeding is reached. Follow the instructions on the bag for the right amount of Critical Care to administer that will be based on your pet’s weight. Be careful when syringe-feeding any animal to avoid them aspirating the fluid. You may want to get instructions from a vet.
How to Syringe Feed
- Try to hold your iguana at a 45 degree upward angle on your arm or have someone help you.
- Gently pull down on the upper portion of the dewlap closest to the jaw and gently press the syringe against the mouth to part it open.
- Try to place the syringe towards the back of the throat so you can slowly push all the material down the esophagus.
- Hold your iguana in the upright position to allow it to swallow and gently place it back down.
Iguanas require a specific ratio of calcium and phosphorus in order to prevent problems like calcium binding , so when offering other foods that aren't staple greens, they should be in lower amounts in every meal. Generally the foods that are higher in protein and calories are those that cannot be fed in excess, so be sure to abide by the feeding guidelines outlined in this article and other sources.
According to Dr. Gina Calvo Sandor, a veterinarian who is an active member of the Association of Reptile and Amphibian Veterinarians, studies suggest iguanas in the wild select younger leaves with a higher crude protein content and avoid mature leaves with a lower crude protein content , while iguana owners mostly feed their iguanas mature leaves that are high in fat, lower in fiber, too high in carbohydrates, and variable in protein. It may be a good idea to select younger plants (but not very young sprouts) such as what is commonly referred to as baby greens in the grocery store. The usual recommendations for the calcium:phosphorus ratio apply, so lettuces should be fed sparingly. Instead, search for young dark leafy greens.
This is a good source of protein that adds some great variety to your iguana's diet. The best way to offer alfalfa to iguanas is by using alfalfa-based rabbit pellets. Some commercial iguana diets also include this as a base. Fresh alfalfa sprouts can be offered, but there is some concern that those which are sold in stores can be contaminated with salmonella and E.coli. The mature alfalfa found in pellets contains more nutrition as well . Growing your own sprouts is another option. Alfalfa pellets should compose less than 5% of the diet .
Legumes, Beans, Chickpeas and Lentils
These are plant-based foods that are higher in protein that can be occasionally added to your iguana's salad. These foods are especially beneficial for juveniles . They should be cooked.
Some Plant Foods With More Calories (Per 100 Grams)
Here's a list of vegetable and plant-based foods in order from highest to lowest caloric value. Be sure to change things up and keep these foods in the appropriate amounts.
- Corn (365 calories)
- Sweet Potatoes (86 calories)
- Peas (81 calories)
- Parsnips (75 calories) Staple Veggie
- Chicory (72 calories) Staple Green When Mixed
- Kale (49 calories)
- Squash (45 calories) (acorn, butternut and kabocha are staple veggies)
- Brussel Sprouts (43 calories)
- Carrot (41 calories)
- Broccoli (34 calories)
- Okra 33 (calories) Staple Veggie
- Collard Greens (32 calories) Staple Green
- Green Beans (31 calories) Staple Veggie
- Mustard (27 calories) Staple Green
- Pumpkin (26 calories)
Fruits With More Calories (Per 100 Grams)
Fruits are high in phosphorous and should be used sparingly. Commercial fruits are also lower in protein and calcium .
- Persimmon 127 calories)
- Plantains (122 calories)
- Banana (89 calories)
- Pomegranate (83 calories)
- Figs (74 calories)
- Grapes (69 calories)
- Kiwi (61 calories)
- Mango (60 calories)
- Blueberry (57 calories)
- Pear (57 calories)
- Allen, Mary E., and Olav T. Oftedal. "Nutrition in captivity." Husbandry and Veterinary Management of the Green Iguana (2003)
- Crutchfield, Tom. “Green Iguana Care Sheet” (On-line), Reptiles Magazine. Accessed July 28, 2019 at http://www.reptilesmagazine.com/Care-Sheets/Lizards/Green-Iguana/
- “Feeding Iguanas” (On-line), Green Iguana Society. Accessed July 28, 2019 at http://www.greenigsociety.org/feedingigs.htm
- “Food Information Chart” (On-line), Green Iguana Society. Accessed July 28, 2019 at http://www.greenigsociety.org/foodchart.htm
- “Fruit Calories” (On-line), Calories.info. Accessed July 28, 2019 at https://www.calories.info/food/fruits
- Gibbons, Paul. "CRITICAL CARE NUTRITION AND FLUID THERAPY IN REPTILES". Avian and Exotic Vet Care. Accessed July 28, 2019 at https://www.avianexoticvetcare.com/userfiles/Reptile_Critical_Care_IVECCS_2009.pdf
- Gingell, F. 2005. "Iguana iguana" (On-line), Animal Diversity Web. Accessed July 28, 2019 at https://animaldiversity.org/accounts/Iguana_iguana/
- Horton, Susan. “Green Iguana Care” (On-line), Chicago Exotics Animal Hospital. Accessed July 28, 2019 at http://www.exoticpetvet.com/green-iguana-care.html
- Kaplan, Melissa. "Fluids and Fluid Therapy in Reptiles". Fluids and Fluid Therapy in Reptiles. (On-line) Acessed July 28, 2019 at http://www.anapsid.org/fluids.html
- Kaplan, Melissa. "The Facts About Alfalfa". Melissa Kaplan's Herp Care Collection. (On-line) Acessed July 28, 2019 at http://www.anapsid.org/fluids.html
- “Miscellaneous Conditions” (On-line), Green Iguana Society. Accessed July 28, 2019 at http://www.greenigsociety.org/miscconditions.htm#dehy
- “Vegetable Calories” ” (On-line), Calories.info. Accessed July 28, 2019 at https://www.calories.info/food/vegetables
- Troyer, Katherine. "Diet selection and digestion in Iguana iguana: the importance of age and nutrient requirements." Oecologia 61.2 (1984): 201-207.
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.