Reptile nutrition guide: gecko, bearded dragon, snake, tortoise
Reptile pets are among the companion animals with the widest gap between ideal and actual diet. This is not a lack of available information - it is a combination of persistent myths, incorrect information from pet shops, and a deep misunderstanding of reptile biology. The result: Metabolic Bone Disease (MBD) is described by specialist veterinarians as the leading cause of death in captive reptiles.
This guide covers the four most common pet reptile species in Europe and North America: the leopard gecko, the bearded dragon, the ball python and the tortoise. For each species, we detail specific nutritional needs, critical mistakes to avoid, essential supplements, and rated product recommendations. For the complete list of reptile foods we have evaluated, see our best reptile food page. The French version of this guide is available at /fr/blog/fr-alimentation-reptile-guide/.
The basics: why reptiles are nutritionally different
Before the species details, it is important to understand what fundamentally distinguishes reptiles from mammals in nutritional terms.
Ectothermic metabolism and nutrient absorption
Reptiles are ectotherms: they do not generate body heat through metabolism. Their body temperature depends on the environment. This has direct nutritional consequences: a reptile at too low a temperature does not digest efficiently. Digestive enzymes function within a specific thermal range. A leopard gecko fed at 20°C instead of 28-30°C may present the same signs as an underfed animal even with a correct ration.
In other words: before modifying the diet of a reptile showing deficiency signs, always check terrarium temperatures first.
The calcium:phosphorus ratio: the most critical parameter
The calcium:phosphorus ratio is the single most important nutritional parameter for all captive reptiles. The optimal ratio sits between 2:1 and 1:1 (calcium:phosphorus). An inverted ratio (more phosphorus than calcium), common in unsupplemented diets, causes progressive bone resorption: the body withdraws calcium from bones to maintain blood calcium homeostasis. This is MBD.
Most feeder insects have an unfavourable calcium:phosphorus ratio (approximately 1:3). They must be dusted with a calcium supplement before each feeding for insectivorous reptiles. Leafy greens (dandelion, clover, lamb's lettuce) have a favourable ratio (2:1 or better).
| Food source | Approximate Ca:P ratio | Supplement required |
|---|---|---|
| Unsupplemented crickets | 1:3 | Yes - calcium D3 powder |
| Gut-loaded crickets | 1:1.5 | Yes - calcium powder |
| Mealworms | 1:20 | Yes (very unfavourable ratio) |
| Dandelion leaves | 3:1 | No |
| Kale | 2:1 | No |
| Sweet potato | 1:1 | No |
| Frozen rodents | 1:1 | No |
Leopard gecko (Eublepharis macularius)
The leopard gecko is one of the most popular pet reptiles in Europe, especially among beginners. Its reputation as an "easy reptile" is justified in some respects - it is robust, tameable, and tolerates temperature errors better than some species. Nutritionally, it is less forgiving.
What it eats: strict insectivore
The leopard gecko is a strict insectivore. It does not consume plants. Its captive diet must consist exclusively of live insects, varied and gut-loaded.
Gut-loading: feeding insects nutritious foods (fresh vegetables, oats, spirulina) for 24 to 48 hours before giving them to the gecko. A cricket that has itself eaten broccoli and carrots delivers far more beta-carotene and calcium than a cricket kept on dry bread or standard feeder chow.
Recommended feeder insects by nutritional quality:
| Insect | Protein (DM) | Fat (DM) | Recommended frequency |
|---|---|---|---|
| House cricket (Acheta domesticus) | 64 pourcent | 18 pourcent | 2-3x/week (juvenile: daily) |
| Dubia roach (Blaptica dubia) | 61 pourcent | 22 pourcent | 2-3x/week |
| Mealworm (Tenebrio molitor) | 52 pourcent | 35 pourcent | Max 1x/week (obesity risk) |
| Superworm (Zophobas morio) | 48 pourcent | 40 pourcent | Occasional (high fat) |
| Hornworm (Manduca sexta) | 52 pourcent | 17 pourcent | Good complement |
Supplementation: mandatory at every feeding
- Calcium powder without D3: dust all insects at every meal
- Calcium powder with D3: once per week (if no UVB lighting)
- Multivitamin powder: once per week
If the enclosure has quality UVB lighting (Arcadia T5 6 pourcent), the D3 powder frequency can be reduced. Leopard geckos are crepuscular/nocturnal and synthesise little D3 from light in the wild - but recent studies (Ferguson et al., 2010) indicate that moderate UVB exposure improves their calcium balance.
Bearded dragon (Pogona vitticeps)
The bearded dragon is the reptile species whose nutritional needs change most dramatically over its lifetime. A juvenile bearded dragon and an adult bearded dragon eat what are essentially opposite diets.
Juvenile (0 to 6 months): 80 pourcent insects / 20 pourcent vegetables
Juveniles have high protein needs to support rapid growth. The diet should consist of:
- 70 to 80 pourcent gut-loaded insects (small-size crickets, dubia roaches)
- 20 to 30 pourcent finely chopped leafy greens (dandelion leaves, kale, lamb's lettuce)
- Calcium + D3 supplementation at every feeding
- Twice-daily feeding (fast metabolism)
Adult (over 18 months): 80 pourcent vegetables / 20 pourcent insects
| Component | Recommended share | Examples |
|---|---|---|
| Leafy greens | 50 pourcent | Dandelion, kale, lamb's lettuce, clover, spinach (limited) |
| Root vegetables/fruits | 20 pourcent | Carrot, squash, bell pepper, blueberries |
| Insects | 20 pourcent | Dubia, crickets, mealworms (limited) |
| Edible flowers | 10 pourcent | Dandelion, clover, hibiscus |
What to never feed a bearded dragon:
- Iceberg lettuce (95 pourcent water, zero nutritional value, causes diarrhoea)
- Excess spinach (oxalic acid chelates calcium)
- Onions, leeks, garlic (toxic)
- Avocado (toxic to all reptiles)
- Wild-caught insects (parasite and pesticide risk)
- Fireflies (Photinus spp.): absolutely lethal to bearded dragons even in tiny quantities
UVB: indispensable and non-substitutable
The bearded dragon is a diurnal species from the Australian desert that receives extremely high doses of UVB radiation in its natural habitat. In captivity, it requires powerful UVB lighting (Arcadia T5 12 pourcent or Ferguson Zone 4 equivalent) to synthesise adequate vitamin D3. A dietary D3 supplement alone is insufficient for bearded dragons - overdose risk is real and effectiveness is far lower than cutaneous synthesis.
Ball python (Python regius)
The ball python is the most popular pet snake in Europe. Its appeal comes from its calm temperament and manageable size (1 to 1.5 metres average). Nutritionally, it is the simplest captive reptile to feed correctly.
Diet: whole frozen-thawed prey
The ball python is a strict carnivore. Its diet must consist exclusively of whole prey items - whole prey delivers all necessary nutrients in the correct proportions (muscle, bone, organs, fat, fur). A snake fed whole prey requires no supplementation whatsoever.
The golden rule: freeze-thaw before feeding. Live prey is dangerous (bite injuries), stressful for the animal, and raises ethical concerns. Freshly killed prey can transmit pathogens. Prey frozen for at least 3 days eliminates the majority of parasites and pathogenic bacteria.
| Life stage | Prey size | Frequency |
|---|---|---|
| Juvenile (0-6 months) | Pinky mice | Every 5-7 days |
| Sub-adult (6-18 months) | Adult mice | Every 7-10 days |
| Adult (18 months+) | Medium rats | Every 10-14 days |
| Large adult (1.2m+) | Large rats | Every 14-21 days |
The correct prey size indicator: the bulge visible in the snake's body after ingestion should not exceed 1.5 times the snake's maximum body diameter. A prey item that is too large causes regurgitation and digestive stress.
Feeding refusal: when to worry
Ball pythons are known for seasonal feeding refusals that can last weeks to months, particularly in autumn and winter. An adult in good body condition can fast for 3 to 4 months without a medical problem. A juvenile refusing food for more than 3 weeks warrants a veterinary consultation. Common causes of prolonged refusal outside the seasonal cycle: inadequate temperatures, environmental stress, internal parasitism, dehydration.
Tortoise (Testudo hermanni, Testudo graeca)
Tortoises are the reptiles most frequently mistreated through their diet by uninformed owners. Classic mistakes (excess fruit, iceberg lettuce, supermarket salad-based feeding) account for the majority of veterinary consultations for this species.
Diet: strict herbivore, high fibre, low sugar
Testudo species are strict herbivores whose natural diet consists primarily of wild Mediterranean plants: dry grasses, clover, dandelion, mallow, plantain. These plants share key characteristics: high fibre, low sugar content, favourable calcium:phosphorus ratio.
The basic framework for an adult tortoise:
| Component | Share | Examples |
|---|---|---|
| Wild plants | 60 pourcent minimum | Dandelion, clover, plantain, mallow, oregano |
| Leafy vegetables | 25 pourcent | Kale, lamb's lettuce, rocket, chicory |
| Root vegetables/flowers | 15 pourcent | Squash, carrot (limited), dandelion flowers |
| Fruit | 0-5 pourcent maximum | Only in autumn for Mediterranean species |
What to never feed a tortoise:
- Excess fruit: simple sugars disrupt intestinal flora and cause bloating and diarrhoea. A Hermann's tortoise does not eat strawberries in the wild in July - the temptation to "treat it" is understandable but medically problematic.
- Iceberg lettuce: no nutritional value, excessive water dilutes electrolytes
- Spinach, beetroot: high oxalic acid
- Animal protein: Testudo species are not omnivores. Regular animal protein (cat biscuits, meat) causes irreversible visceral gout (renal calcification) over time.
- Potatoes, avocados, onions: toxic
Hibernation and nutrition
Testudo species hibernate naturally between November and March. Before hibernation, the tortoise must be in good body condition (not obese, not too thin) and have emptied its digestive tract (3-4 weeks of fasting at decreasing temperatures). An undernourished tortoise should not be put into hibernation - the risk of death from hypoglycaemia or renal failure during the cold phase is high.
Supplements: which ones, how and when
Calcium D3 (Arcadia EarthPro-CalciumPro Mg, Zoo Med Repti Calcium)
Calcium supplement with vitamin D3 is mandatory for all captive insectivore or herbivore reptiles without access to quality UVB lighting. It comes as a fine powder dusted directly onto insects or vegetables before each feeding.
For reptiles with quality UVB lighting, a D3-free version can be used daily and the D3 version reserved for once a week to avoid vitamin D3 overdose (hypervitaminosis D).
Multivitamins (Herptivite, Arcadia EarthPro RevitaliseD3)
Weekly multivitamin supplementation covers potential gaps in vitamins A, E and B-complex. It does not replace a varied diet but provides a safety net.
Top reptile supplement brands compared
| Brand | Product | Score | Composition | Price |
|---|---|---|---|---|
| Arcadia | EarthPro-CalciumPro Mg | A (90/100) | Calcium gluconate, magnesium, titrated D3 | 12 euros / 50g |
| Zoo Med | Repti Calcium with D3 | A- (86/100) | Calcium carbonate, D3 | 8 euros / 90g |
| Repashy | Calcium Plus LoD | A- (85/100) | Calcium, multivitamins, low-dose D3 | 18 euros / 84g |
| Exo Terra | Calcium + D3 | B+ (78/100) | Adequate composition, less titrated D3 | 7 euros / 90g |
| Komodo | Calcium Supplement | B (74/100) | Calcium carbonate, D3-free | 5 euros / 225g |
Arcadia is the reference brand in the UK and Europe for reptile supplements. Their formulas include calcium gluconate (better bioavailability than carbonate) and magnesium, often omitted in competing formulas.
Repashy deserves a special mention: the company also offers complete food supplements in gel form (Crested Gecko MRP, Grub Pie) that partially replace insects and simplify feeding for crested geckos and other omnivorous species. These products earn an A rating on our reptile food page.
Hydration: often overlooked
Snakes
Pythons and boas must have access to fresh water at all times. They will sometimes bathe in it - this is normal behaviour. The water bowl must be cleaned and refilled at least twice a week.
Leopard geckos
Leopard geckos hydrate primarily through their prey but must have access to a small fresh water dish. In dry enclosures (under 40 pourcent humidity), light misting of the terrarium walls at night can be beneficial.
Bearded dragons
Bearded dragons drink rarely but are not so desert-adapted that they never drink. A shallow water dish changed daily is sufficient. Light misting of vegetables and terrarium walls in the evening can also stimulate water intake.
Tortoises
Tortoises should have access to a shallow bath 1 to 2 times per week, especially during hot periods. They hydrate primarily by drinking during these baths. Some individuals rarely drink in captivity - fresh watery vegetables (cucumber, courgette as a supplement) can partially compensate.
Recognising and treating MBD early
Metabolic Bone Disease is not binary - it exists on a spectrum. Recognising the early signs and acting quickly can prevent permanent deformity.
Early signs of MBD:
- Slight tremors or twitching of limbs at rest (hypocalcaemic tetany)
- Reluctance to climb or use full range of motion
- Slight softening of the jaw (in bearded dragons, the lower jaw may appear rubbery)
- Reduced appetite without other obvious cause
- In tortoises: soft or pyramiding shell
Intermediate signs:
- Visible limb deformity (bowed legs, curved spine in young bearded dragons)
- Pathological fractures (fractures without obvious trauma)
- Constipation from weak gut musculature
Treatment approach: MBD diagnosed early responds well to treatment: correcting the thermal gradient, initiating or improving UVB provision, increasing calcium supplementation frequency, and in acute cases, veterinary-administered calcium gluconate injections. A veterinarian specialising in exotic animals should be consulted for any suspected MBD case. At-home supplementation alone is insufficient once visible deformity has occurred.
For context on how other species manage calcium and bone health, see our guinea pig nutrition guide covering the specific calcium needs of small herbivore mammals.
Choosing and reading reptile food labels
Not all reptile foods are equal and the label can be deceptive. For a full guide to reading any pet food label, see our pet food label guide. For reptile-specific considerations:
Gut-load food: The label of a feeder insect gut-load product should list vegetable and grain ingredients rather than generic "grain products." A gut-load based on spirulina, kale powder, dandelion and oats will deliver far more bioavailable calcium and beta-carotene than one based on corn and wheat filler.
Complete reptile food (for omnivores): Products marketed as "complete bearded dragon food" or "complete tortoise diet" exist but must be scrutinised carefully. A complete diet for a bearded dragon adult should list leafy greens or grasses as primary ingredients, not corn starch or dried peas. Calcium content on a dry matter basis should be at or above 1 pourcent; phosphorus at or below 0.8 pourcent.
Supplement labels: The D3 content in a calcium supplement matters. Products with "D3" in the name vary widely in their actual cholecalciferol content per gram. Arcadia EarthPro-CalciumPro Mg lists specific IU/kg values; many competitors do not. When the D3 content is unstated, you have no way to calibrate the dose.
For our full ranked comparison of reptile supplements and complete foods, see the reptile food rankings on PetFoodRate and our methodology page.
Most common reptile feeding mistakes
1. Feeding without calcium supplementation. This is the single most frequent direct cause of MBD. A leopard gecko fed crickets without calcium powder for 6 months will show visible clinical signs.
2. Using mealworms as the dietary base. Mealworms (Tenebrio molitor) have a calcium:phosphorus ratio of 1:20 and high chitin content that makes them difficult to digest. They should be an occasional supplement, not the dietary base.
3. Giving excess fruit to tortoises. Sugar disrupts the intestinal flora of Testudo species that evolved on a near-zero sugar diet. Repeated episodes of diarrhoea from excess strawberries or mango can lead to chronic dysbiosis.
4. Not gut-loading insects. A cricket kept without food for 48 hours before being fed to the gecko has lost most of its nutritional value. Gut-loading is not optional.
5. Ignoring the thermal gradient. A reptile that cannot reach its Preferred Optimal Temperature Zone (POTZ) does not digest, does not metabolise supplements, and may show deficiency signs even with a high-quality diet.
Our full selection
For the complete list of reptile foods, supplements and care products we have rated, with ingredient analyses and A-E grades, visit our dedicated page: best reptile food.
Also explore:
- Our methodology page to understand how we evaluate products
- Our overall rankings for the best brands across all species
- Our bird nutrition guide for avian species
- Our ferret nutrition guide for obligate carnivores
- Our how to read a pet food label guide
Sources
- Ferguson GW, et al. Ultraviolet exposure and vitamin D synthesis in a sun-seeking lizard, the bearded dragon. Physiological and Biochemical Zoology, 2005; 78(5): 827-836.
- Donoghue S. Nutrition of pet amphibians and reptiles. Seminars in Avian and Exotic Pet Medicine, 2006; 15(3): 134-148.
- Mader DR. Reptile Medicine and Surgery. 2nd edition. Saunders Elsevier, 2006. Chapter 18: Nutritional diseases.
- Stahl SJ. Reptile nutrition. In: Quesenberry KE, Carpenter JW (eds). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. 3rd edition. Saunders Elsevier, 2012.
- Rosenthal KL. Metabolic bone disease in reptiles. Veterinary Clinics of North America: Exotic Animal Practice, 2004; 7(3): 761-779.
- Arcadia Reptile. Guide to supplementation and UVB lighting. 2023. https://www.arcadiareptile.com/lighting/
- Sophie Lefevre, Species Nutrition Specialist, PetFoodRate