Leopard Gecko Impaction: Causes, Signs, and Prevention

What impaction is

Impaction is a blockage in the digestive tract. Material the gecko cannot pass, substrate, undigested exoskeleton, or hardened waste, packs into the gut and stops things moving. Because a reptile's digestion is slow and entirely dependent on temperature, a blockage that would clear in a mammal can sit and worsen. Left long enough it stops the animal feeding, and it can be fatal.

That is why the fear is justified. Where the standard advice goes wrong is in naming the culprit.

The substrate myth, and the part of it that is true

The claim that loose substrate causes impaction does not hold up on its own. Geckos ingest small amounts of substrate incidentally while hunting, and a well-kept animal passes it without drama. What the evidence and experienced keepers both point to is that impacted geckos are nearly always geckos with something else wrong, which is the position we take in our leopard gecko substrate guide as well.

The part that is true is that some substrates are bad on their own terms and should be avoided outright. Calcium sand is the worst offender, because it is marketed as digestible and tastes appealing enough that geckos eat it deliberately. Walnut shell is sharp and does not break down. Pine and cedar shavings give off oils that are harmful to reptiles. Avoiding those is not superstition, it is just correct. A plain soil and sand mix, or a clay-based burrowing substrate, is a different proposition.

What puts a gecko at risk

• A warm side that is too cool. This is the big one. Digestion is temperature driven, and a gecko kept below its target cannot process a meal. Aim for a floor temperature of about 88 to 92 degrees on the warm end, measured on the surface, not the air.
• Dehydration. Gut contents move on moisture. A gecko without constant clean water and a humid hide to use is far more likely to bind up, which is why chronic low humidity and impaction turn up together.
• Calcium deficiency. A gecko short on calcium will actively seek out and eat mineral substrate, turning incidental ingestion into deliberate mouthfuls. This is the mechanism behind most sand-eating, and the fix is proper supplementation, not just changing the floor.
• Prey that is too large. The standard rule is nothing wider than the space between the gecko's eyes. Oversized insects, and hard-shelled feeders like superworms in quantity, are harder to digest and more likely to cause a problem than the substrate underneath.
• Underlying illness. Parasites and other health problems slow the gut down on their own. A gecko that impacts repeatedly on a correct setup needs a vet workup, not another substrate change.

Warning signs to act on

Catch it early and it is usually manageable. The first things to notice are a gecko that has stopped passing waste on its normal schedule, has gone off food, or has become noticeably lethargic. A bloated or swollen-looking belly and visible straining are the next stage.

The signs that mean this is no longer a home problem are a dark spot showing through the belly or side, eyes that stay barely open, a tail that is visibly thinning as the animal burns reserves, and severe lethargy. Those need a reptile vet the same day, not next week, because a blocked gecko cannot absorb food or water and goes downhill fast.

What to do, and where home care stops

If you suspect a mild, early impaction, the useful steps are the boring ones. Correct the warm side temperature first, because nothing else works without it. Offer a shallow, lukewarm soak at around 85 degrees to hydrate the animal and encourage it to pass. Make sure clean water is always available, hold off on feeding until the gecko passes waste, and give it a humid hide.

What we would not do is escalate. Oil dosing and forceful belly massage get passed around online, and both can go wrong in ways a keeper cannot undo, so they belong with a vet who can assess the animal first. If a couple of days of corrected temperatures, hydration and soaking produce nothing, or if any of the advanced signs above appear, stop experimenting and book the appointment. A vet can image the blockage and treat it with fluids or, in severe cases, intervene surgically, and that decision needs to be made before the gecko is too weak. That is worth picturing, because it is not a scaled-up version of the home steps: an x-ray to confirm there is a blockage and not eggs or something else, then a prescribed course aimed at moving it. That is a different thing from dosing oil at home and hoping, and it is the reason the honest advice is to stop and go rather than to keep escalating yourself.

Building the dig mix, and keeping it clean

If you are mixing your own substrate, the bag matters more than the ratio. A lot of what is sold as topsoil or planting mix is not plain dirt: it carries fertilizer, perlite, water-retention crystals or composted manure, and none of those belong in an enclosure where the animal will take an occasional mouthful. Read the ingredients and buy the boring bag with nothing added. This is the one place we would not improvise.

Sterilizing a homemade mix before it goes in is worth the afternoon. Bagged soil arrives with fungus gnat eggs in it, and keepers who skip this step tend to find out a fortnight later when the enclosure has a resident population. Spreading the mix on a tray and baking it kills what is in there.

We would also stage it rather than redo the whole floor at once. A dig box, a tub of damp mix set into the enclosure, lets you see how your gecko treats loose substrate before you commit the entire base to it. If the animal digs and does not eat the stuff, expanding to a full substrate is a smaller decision.

Then keep it clean, because a soiled substrate is a genuine risk in a way a clean one is not. On a non-bioactive setup that means lifting waste out daily and replacing the whole lot a few times a year. A bioactive setup with a working cleanup crew handles the breakdown itself, which is most of its appeal.

Preventing it: the setup, not the paranoia

Prevention is unglamorous. Get the warm side floor into the high 80s and verify it with an infrared temp gun, not a stick-on dial. Keep water available and give the gecko a humid hide, which is the same fix that prevents stuck shed. Dust feeders with calcium on the schedule your lighting setup calls for. Feed appropriately sized prey. Choose a safe substrate and skip the few that are dangerous on their own terms.

Do that and loose substrate stops being the thing keeping you awake, because you have removed the conditions that turn a mouthful of soil into a blockage. Bare paper towel is a reasonable choice for a quarantine tank or a sick animal, but a healthy gecko on correct husbandry does not need to live on kitchen roll for life.

Our call

Impaction is a husbandry failure that shows up in the gut, not a curse cast by loose substrate. The geckos that get it are usually too cool to digest, dry, short on calcium, or eating prey too big for them. Fix those and the risk drops to something close to background noise.

Avoid calcium sand, walnut shell, and pine or cedar, since those are bad on their own terms. Then spend your attention on the warm side temperature and a temp gun to confirm it, because that single number does more to prevent impaction than any substrate swap.