Health guide, not a diagnosis · Serious if left

Soft shell & metabolic bone disease

Also called metabolic bone disease (MBD), secondary nutritional hyperparathyroidism (veterinary name), soft shell (hobby name)

Can spread to people. Human-health risk: turtles of any size can carry Salmonella in their droppings even when they look healthy and clean; the germs spread to their bodies, tank water and anything around them, and a vet cannot stop a turtle from shedding them. Wash hands with soap and water right after touching or feeding the turtle or cleaning its tank; don't kiss or snuggle it, don't eat or drink around it, keep it and its equipment out of the kitchen. CDC does not recommend turtles for households with children under 5, adults 65 and older, or people with weakened immune systems. Sale of turtles with shells under 4 inches (about 10 cm) has been banned in the USA since 1975.

Facts checked against sources on 16 Oct 2026. See sources

Signs

Misshapen or deformed shell
Deformed legs, weakness, unable to walk normally
Slow growth
Swollen or distorted jaw; fractures
Poor appetite, lethargy, muscle twitching

Cause

Calcium-phosphorus imbalance: a diet too low in calcium relative to phosphorus and lacking vitamin D3, and/or too little UVB light (needed to make vitamin D3 for calcium absorption) and inadequate heating. Mostly affects fast-growing young turtles.

What to do

See a reptile vet (X-rays and blood tests confirm it; severe cases need fluids, nutritional support and calcium injections). Correcting the diet and husbandry, including proper UVB, is the main treatment; prognosis is good if the turtle is still eating. Some vets suggest a calcium block or cuttlebone about twice a week.

If a fish is badly ill, talk to an aquatic vet.

Prevention

A UVB lamp (290-320 nm) over the basking spot, about 30-45 cm from the turtle, with no glass or plastic in between; replace it every 6 months or as the manufacturer directs, because UV output falls with age. Unfiltered outdoor sunlight when weather allows. A balanced diet with a calcium source.