Almost every insect sold as a feeder contains more phosphorus than calcium, which is the opposite of what a growing reptile needs. This guide covers what the published ratios actually are, why the figure for the same species varies between papers, what the ratio can be moved to, and which methods have been shown to move it.
Why the ratio matters more than the calcium figure alone
Calcium and phosphorus compete. A diet can contain adequate calcium in absolute terms and still leave an animal short, because excess dietary phosphorus interferes with how much of that calcium ends up available. This is the mechanism behind nutritional secondary hyperparathyroidism, the bone disease often called metabolic bone disease. The Merck Veterinary Manual lists a poor calcium to phosphorus ratio, low vitamin D3, lack of UVB light and too little heat among its causes.
None of that is something to self-diagnose. If an animal stops eating, has a swollen jaw or limbs, twitches, or cannot walk normally (signs the Merck Veterinary Manual associates with the disease), that is a same-week appointment with an exotics vet, not a supplement adjustment. What the ratio is useful for is prevention, and prevention is entirely a husbandry question.
What the ratio is in common feeders
The figures below are as published. Each row names what was actually measured, because "the Ca:P of a cricket" is not one number and treating it as one is how bad charts get made. We have not measured any of this ourselves.
| What was measured | Reported Ca:P | Kind of source |
|---|---|---|
| Commercially raised feeder insects, as a group | 0.28:1 or lower | Summary across species in a widely cited composition study |
| Black soldier fly larvae | about 2.5:1 | Same study, named as the single exception |
| Dubia roach nymphs | 0.35:1 | Single published analysis |
| Dubia roach adults | 0.26:1 | Same analysis |
| Dubia roach adults, across several studies | 0.04:1 to 0.40:1 | Range quoted in a 2025 review of prior work |
| House crickets, undusted controls | 0.34:1 | Gut-loading trial, control group |
| Field crickets, fasted, all instars pooled | 0.14:1 mean | Dusting trial, control group |
| Silent crickets, fasted, all instars pooled | 0.25:1 mean | Same trial |
The pattern is consistent even where the numbers are not. Everything on that list except the soldier fly larva is inverted, most of it badly. A ratio of 0.14:1 means roughly seven times as much phosphorus as calcium.
The one feeder that starts out right, and its catch
Black soldier fly larvae are the exception, and they are the exception for a physical reason: they lay down calcium in the cuticle rather than merely carrying it in the gut. That makes their ratio a property of the animal rather than of what it last ate, which is why it holds up when other feeders' ratios do not.
The catch is absorption. A feeding trial in leopard geckos measured dry matter digestibility of whole soldier fly larvae at around 71%, but calcium digestibility at only around 43%. Related work in frogs found calcium digestibility of around 44% for whole larvae against around 84% for dusted crickets, and mashing the larvae raised it substantially. The calcium is there. A meaningful share of it goes straight through. So soldier fly larvae are a good part of a rotation rather than a reason to stop supplementing. You will find our black soldier fly larvae alongside the other larval feeders on our feeders page.
What to aim for
The target quoted in the zoo and veterinary nutrition literature is a dietary ratio somewhere between 1:1 and 2:1 in favor of calcium, with 2:1 the figure most often named for insectivorous reptiles.
Two things are worth saying plainly about that target. It applies to the whole diet, not to every individual insect. And it is a range in the sources, not a single agreed value, which is why you will see 1:1, 1.5:1 and 2:1 quoted with equal confidence on different sites.
Moving the ratio, and what fails to move it
There are two levers, and the published evidence is more specific about them than the marketing on either.
- Gut loading with a genuinely high-calcium diet works. A 2025 trial fed dubia roaches a diet containing about 8.3% calcium on a dry matter basis. Nymphs went from around 0.14:1 fasted to around 1.5:1 after 24 hours. Adults reached around 5.1:1 after one day. That is a real correction, from a real measurement.
- Gut loading with a diet that is not actually high in calcium does not work. The same trial's low-calcium diet, sold as an all-in-one insect diet, left nymphs at around 0.19:1 after 24 hours, which is no better than fasted. Earlier work testing calcium-fortified high-moisture cricket diets found control crickets at 0.34:1 and crickets gut-loaded for 48 hours at 0.31 to 0.32:1. Several of those products carried claims about shifting the ratio toward 2:1. They did not.
- Dusting works, and lasts longer than commonly claimed. A trial dusting two cricket species found every dusted cricket above 1:1 at every sampling point out to 5.5 hours, with hatchlings staying above 4:1. Adult field crickets were the weakest, barely holding 2:1 immediately after dusting, most likely because the adult cuticle is hard and smooth and holds less powder.
The practical reading is that the label on a gut-loading product is not evidence, and that a diet needs a calcium content in the high single-digit percentages on a dry matter basis to shift an insect's ratio at all. Whether a specific product does what it claims is a question for its own analysis panel.
Where the published figures disagree, and why
Fasting
An insect analyzed straight from the tub includes its gut contents. An insect fasted for 24 hours does not. The 2025 roach trial found dubia need longer than 24 hours to empty completely, so even a fasted figure may not be a clean one. Studies that skip fasting are measuring what your animal actually eats, which is arguably the more useful number, but it is not comparable to a fasted one.
Where the insects came from
The same roach trial recorded fasted adult controls at 1.6:1, well above the 0.04:1 to 0.40:1 reported elsewhere for adult dubia. The authors' own explanation was that those roaches came from a maintenance bin where some had probably been gut-loaded already. That is worth remembering: a feeder's ratio partly reflects a breeder's colony diet, which nobody publishes.
Life stage
Nymph and adult figures differ within the same species, and dusting behaves differently across instars. A guide that gives one ratio for "roaches" or "crickets" is compressing something real.
What to actually do
Feed a rotation rather than one species, gut load on something with a stated calcium percentage rather than a claim, dust according to the supplement's own instructions, and get UVB and temperatures right, because none of the above compensates for a reptile that cannot use the calcium it eats. Talk to an exotics vet about supplementation schedules for your particular animal.
Side-by-side figures for the common feeders, Ca:P included, are in the nutrition table of our bearded dragon feeder guide. For the two levers in detail, read how to gut load feeder insects and dusting feeders with calcium and vitamins. If you are choosing a staple, dubia roaches and crickets are the two most commonly used. We do not sell crickets; dubia roaches are what we sell instead. Background on the rest of the numbers is in feeder insect nutrition explained.