Tortoise supplement
Tortoises are mostly herbivorous grazers, and their natural diet of weeds, flowers and leafy plants is far higher in calcium relative to phosphorus than the fruit and vegetables most owners actually have easy access to. A calcium supplement, dusted onto food regularly, is how that gap usually gets closed in captivity.
Why tortoises specifically need extra calcium
Calcium is essential for shell growth and strength as well as bone health, and a tortoise that consistently gets too little relative to phosphorus can develop metabolic bone disease — a genuinely serious, and largely preventable, condition that causes soft or deformed shell and bone growth. This risk is higher in tortoises than in many other reptiles because of how calcium-dependent their shell development is.
Komodo's Calcium Supplement for Herbivores is formulated specifically for grazing reptiles like tortoises, meant to be lightly dusted onto fresh food rather than given as a separate item on its own. The idea is to top up what a captive diet of shop-bought vegetables and leaves is missing compared with a wild tortoise's natural forage.
Calcium with and without vitamin D3
Some calcium supplements include vitamin D3, which a tortoise needs to actually absorb and use dietary calcium properly, while others are calcium-only, relying on the tortoise producing its own D3 through UVB exposure instead. Which one is appropriate depends on the lighting setup in your tortoise's enclosure, since a tortoise with adequate UVB lighting can be oversupplemented with D3 if it's also getting it through a supplement unnecessarily.
This is worth getting right rather than guessing — an exotics-experienced vet or a specialist reptile source can advise on the correct supplement type and frequency for your specific tortoise, enclosure and lighting setup, since needs vary by species, age and how the animal is housed.
Supplementing alongside fresh food, not instead of it
A supplement tops up a varied diet of fresh, appropriate weeds, flowers and vegetables; it doesn't replace the need for that variety in the first place. A tortoise fed a narrow range of high-water, low-nutrient vegetables like lettuce, with a calcium dusting added on top, is still missing most of what a proper varied diet provides.
Dusting frequency is usually a few times a week rather than every single feed for an adult tortoise, though growing tortoises typically need it more often. Follow the product's own guidance for the life stage of your tortoise, and speak to an exotics vet if you're setting up a new tortoise's diet for the first time.
What we stock
Everything below is in stock with us, priced with delivery worked out, and packed and posted by hand in the UK.
Hagen Exo Terra Daylight Basking Spot
A broad-spectrum daylight basking bulb, providing heat and light for a terrarium
From£8.39
Komodo Tortoise Food Salad Mix
A complete holistic tortoise diet flavoured to taste like fresh salad
£7.29
Monkfield Mouse, Fluff
25 frozen Fluff-stage mice (3-5g each) for reptiles, from a DEFRA-licensed maker
£14.99
Tetra Reptomin Sticks
Complete Tetra ReptoMin dry sticks for water turtles, with calcium and phosphorus
£4.98
Tetra ReptoMin
Floating stick food for water turtles, with 39% protein and added calcium for shell growth
£9.06
Supa Turtle Food Super
A freeze-dried shrimp and tubifex food for turtles, alongside fresh food
From£5.99
Komodo Tortoise Food Dandelion
A complete holistic tortoise diet in dandelion flavour, high in fibre
From£7.29
Komodo Tortoise Food Fruit Flower Flavour
A fruit and flower flavoured tortoise diet, high in fibre with a calcium-forward mineral ratio
From£7.29
Komodo Aspen Bed Terrain
A 6-litre aspen bedding for snakes, built to hold its shape when burrowed into
£6.79
Common questions
- Why do tortoises need more calcium than other reptiles?
- Their shell is made largely of bone and grows throughout their life, which makes calcium intake unusually important compared with reptiles without a shell. A tortoise consistently short on calcium relative to phosphorus is at real risk of metabolic bone disease.
- Does my tortoise need a supplement with vitamin D3 or without?
- It depends on your tortoise's UVB lighting setup — one with good UVB exposure produces its own vitamin D3 and may not need it added through a supplement, while one with limited UVB access may need a D3-inclusive product. An exotics vet can advise on the right choice for your specific setup.
- How often should I dust my tortoise's food with calcium?
- It varies with age and species, with growing tortoises generally needing more frequent supplementation than adults. Follow the guidance on the specific product you're using, and check with an exotics-experienced vet if you're unsure for your tortoise.
- What happens if a tortoise doesn't get enough calcium?
- Long-term calcium deficiency relative to phosphorus can lead to metabolic bone disease, which causes soft, weak or deformed shell and bone growth. It's a serious but largely preventable condition, and a consistent, appropriate calcium supplement alongside a varied diet is the main way to avoid it.
Related
Written by Matt Garnett, who runs Giddy Pets and is a lifelong pet owner — not a vet. This is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your animal. How we write these guides.