Roof Rat Health & Lifespan

Are roof rats healthy and hardy in general?

Generally, yes, they’re hardy little animals. (We haven’t kept fancy rats in a while, so I won’t claim a precise side-by-side, but ours stay healthy.)

Will a roof rat adapt to my daytime schedule?

To some extent. I actually use their natural rhythm to my advantage, they reliably head back to their cage around the same time each day.

Do roof rats need a vet?

Yes, find a vet experienced with exotics or “pocket pets.” This FAQ informs, but it never replaces veterinary care. Any discharge from the eyes, nose, or mouth, or noisy, labored breathing, means a vet visit. See our find-a-rat-vet tool for how to find one near you.

How can I tell if my roof rat is dehydrated?

Two easy checks. First, the skin-pinch test: gently lift the loose skin over the shoulders into a little tent and let go. In a well-hydrated rat it snaps right back flat; if it stays tented and settles back slowly, that points to dehydration. Second, the eyes: a healthy, well-hydrated roof rat has eyes like bright little marbles, kind of bulging out of the head, with a wide-awake, alert look. Sleepy or sunken-looking eyes, along with loose skin and low energy, are warning signs. Keep fresh water available at all times (we like a locking dish), and see an exotics vet if it doesn’t clear up. The photos further down this page show what those bright, healthy eyes look like.

How can I give rats medicine in their drinking water?

It’s probably no surprise that rats generally don’t like taking medicine.  Sometimes, it is easier and less stressful for both you and your rat if you can medicate their drinking water.  This is an option for medicines that dissolve well in water and are stable at room temperature.  Here is the OC Dumbos online rat medicated water dosing calculator.  Please feel free to bookmark and share it.

Because of the small quantities involved, it is sometimes more convenient to pre-mix medicines that some in pills, capsules or packets with water to a specific concentration, so the OC Dumbos dosing calculator allows you to specify how many mg medicine there was per capsule (for example) and how many ml water you pre-mixed it with in a small bottle which you should usually store in your refrigerator.  You would always first shake the bottle to mix the contents, then use a syringe to measure the specified amount from the bottle, and either add it to the drinking water or give it directly to the Rat.

Bottle for pre-mixed medicine

1ml syringe for measuring and giving medicine

How can I give rats medicine orally?

Sometimes medicines will need to be given directly in the rat’s mouth.  For example, Amoxicillin, which does not dissolve well and needs to be refrigerated.  Or if you are not sure the rat will drink a “normal” amount of water from it’s bottle: for example, the rat is too sick or weak, or you are feeding it liquids or mashed foods.  Here is the OC Dumbos online rat oral medicine dosing calculator.  Please feel free to bookmark and share it.

Because of the small quantities involved, it is sometimes more convenient to pre-mix medicines that some in pills, capsules or packets with water to a specific concentration, so the OC Dumbos dosing calculator allows you to specify how many mg medicine there was per capsule (for example) and how many ml water you pre-mixed it with in a small bottle which you should usually store in your refrigerator.  You would always first shake the bottle to mix the contents, then use a syringe to measure the specified amount from the bottle, and either add it to the drinking water or give it directly to the Rat.

Bottle for pre-mixed medicine

1ml syringe for measuring and giving medicine

My rat is sneezing or coughing what can I do?

If your rat is sneezing or coughing, that is a sign of respiratory disease.

If possible, you should take your rat to a vet to have him or her properly diagnosed and treated.  Even mild respiratory disease can develop into something more serious very quickly if left untreated.  A persistent, chronic cough or sneeze is often a sign of Mycoplasma, which can cause permanent loss of lung function.  This will make it harder for your rat to breath and also contribute to other health issues, especially in older rats.  Chronic respiratory disease is probably the leading contributor to shortened lifespan, especially in male rats.

That said, it is not always practical to take your pet to the vet.  So, it is helpful to know some basic remedies that you can try, and have the necessary medicines at hand.  You will need to weigh your rat, and mix these medicines with something tasty at the correct dosage.  The basics are:

Why does my rat smell bad? What can I do about it?

Rats often pee on each other, I guess as a show of dominance or just because they are buddies and they want to mark them. Male rats do this especially, but even females will do so on occasion.

Here is Roofy peeing on Tommy’s back:

I’ve even seen some male Norway rats pee in their own hammock. Not just to mark them, but apparently because they just didn’t feel like getting out of bed to pee at that moment. You can imagine that sleeping in pee doesn’t leave one smelling very good.

Anyway, rat food with Yucca is supposed to help control urine odor.  Oxbow Essentials Regal Adult Rat food has Yucca extract to reduce urine odor. So, if the problem is due to them peeing on each other (or themselves) then at least the pee will be less smelly.

Finally, a high protein diet produces urine with more Nitrogen in it, which will have a stronger odor due to Urea breaking down to ammonia. Adult male Norway rats should be on a lower protein diet anyway, because they will otherwise tend to gain weight as they get older. Roof rats are the opposite, though: they stay lean and stay active, so we keep our roof rats on about 18 percent protein for life and do not cut it as they age. A well fed older roof rat may still put weight on and become less active, so encourage exercise rather than cutting the protein. Overweight rats are more sedentary and likely to pee in their hammocks. They are also generally more unkempt as they will have more trouble reaching all the spots that need cleaning.

So, you should make sure you are feeding adult male Norway rats not more than 16% protein rat food and consider switching to 15-14% protein rat food and see if that helps a bit.  Oxbow Essentials Regal Adult Rat food has 15% protein, so it is a very good choice for a Norway rat. Roof rats are the opposite case described above: Brian keeps his on about 18 percent protein for life.

Why do rats make urine (pee) everywhere?

Just like dogs, often rats urine mark.

They don’t do this because they urgently have to pee, and just cannot hold it in!

Rather, like with dogs, it seems to be a form of social communication and marking of territory.  They seem to be saying “I was here. This is part of my territory.  This belongs to me.”  That thing might be their cage, hammock, toy, or another rat (where it might also be a show of dominance as well as friendship.)

They will even do it to you: I know that sounds kind of gross, but try to take it as a sign of affection!

When you put a rat in a new cage, especially a male, don’t be surprised if the rat immediately starts peeing over every accessible surface.

Male rats do it more than female rats, but both sexes will urine mark.  Roof Rats mark, too, but not as much (they are smaller, which also helps with that!)

Some say that neutering might reduce marking, but I, personally, cannot vouch for that.

How long do roof rats live?

These figures are for Norway rats, not roof rats. They come from an FAQ Brian wrote in 2018, before he kept roof rats, and he filed it under About Rats rather than Roof Rats. For roof rats, Brian’s answer is that they usually live about 3 years and can reach 4 or 5 with good care, longer than a pet Norway rat, and older roof rats seem to have fewer chronic illnesses and tend to stay fairly healthy until the end. Males live about 2 years

Females live about 3 years

They may live longer or shorter depending on care and feeding, and exposure to disease.

How much do rats weigh? (roof rats, and the 2018 Norway rat figures)

These figures are for Norway rats, not roof rats. They were written in 2018 and they describe the fancy-rat weights most references give. Roof rats are smaller, and a roof rat well under the numbers below is not necessarily underweight. Brian’s own roof-rat figures are in the last paragraph. Males are between 350-450 grams full grown. The alpha in the cage will generally grow bigger than the others. They can also get “bigger” if you overfeed them, but that will lead to health issues.

Females are between 250-350 grams full grown. Females are less likely to overeat than males. Females that have raised litters tend to grow larger with each pregnancy due to the hormones.

Roof rats, from Brian’s own colony. A female who is not pregnant usually runs 150 to 270 grams, and a male 230 to 350 grams. He puts the ceiling at 330 grams for a pregnant female and 400 grams for a male, and says neither is usual. He set the pregnant-female ceiling at 330 rather than 320 so that nobody with a heavy pregnant doe worries about her, and he notes he does not remember seeing one that big. These are what he sees in his own animals rather than a published range.

What is the dosage of Ambroxol for Rats by weight?

About 10 mg/kg per day, split into two doses. That figure is Brian’s own: he wrote it in his 2021 Roof Rat care and ownership course, “you could give your Roof Rat about 10 mg/kg per day (roughly 5 mg/kg twice daily) in addition to the antibiotics”, and it replaced the 0.5 to 1 mg/kg twice a day this page gave up to 2020. Give it alongside antibiotics, not instead of them. Ambroxol is well tolerated in children at its usual over-the-counter doses, but as with any medicine an animal can rarely have a serious reaction, so stop and see a vet if anything unusual appears. See, for example:

An overview of efficacy and safety of ambroxol for the treatment of acute and chronic respiratory diseases with a special regard to children

Dosing by weight with a syringe is the most reliable method, since a sick rat may drink less. Splitting the daily amount into two doses, roughly 5 mg/kg each, is his own instruction and not ours: the same sentence of his 2021 lesson gives both the daily figure and the split. Twelve hours apart is our reading of “twice daily”. For a 200 g rat, 10 mg/kg per day comes to 2 mg a day, so about 1 mg per dose. That is about 0.2 ml per dose of a 30 mg tablet dissolved in 6 ml of water, or about 0.3 ml per dose of the pre-mixed 15 mg/5 ml syrup.

Editor’s note, added 2026-08-17. The drinking-water amounts below are our arithmetic, not Brian’s. His own recipe, up to 2020, was 2.5 mg per 250 ml, which went with the lower 0.5 to 1 mg/kg figure he was using then. Turning a dose in mg/kg into an amount per bottle needs a figure for how much a rat drinks in a day, and the sources disagree. Brian looked up 7 to 10 ml per 100 g of body weight, which is 70 to 100 ml per kg. A National Research Council report assumes 30 ml a day for a 300 g rat, which is 100 ml per kg. The table this page has always linked gives 152 ml per kg for an average rat, but that number comes from risk assessment, where the point is to avoid underestimating how much of a contaminant a rat swallows, so it is deliberately set high.

To deliver 10 mg/kg per day, a 250 ml bottle needs about 36 mg of ambroxol at 70 ml per kg, about 25 mg at 100, and about 16 mg at 152. So there is no single right number: the honest range runs from about half a 30 mg tablet to a little over a whole one. If you want one figure to work from, we use 25 mg per 250 ml, on the 100 ml per kg that his own look-up and the National Research Council report agree on. That is about five-sixths of a 30 mg tablet: about 5 ml of a 30 mg tablet dissolved in 6 ml of water, or about 8 ml of the 15 mg/5 ml syrup. Mix it fresh. His note that the taste is not objectionable was written for the 2.5 mg recipe, not for this higher one, so check that your rat is still drinking normally. Because the spread is this wide, treat medicated water as convenience or maintenance and use the syringe when the dose matters. This page previously gave 22 mg per 250 ml; that number was ours as well, and it assumed 114 ml per kg, which is not a figure any source here uses.

Are roof rats prone to tumors like fancy rats?

In our experience, far less often. I almost never see tumors in our roof rats, out of 50+ females, none had visible tumors. One of our males lived to over four years and died of old age, not cancer. I suspect tumors are simply less common in this species.

One likely reason: fancy rats were bred for fast, frequent breeding, and that reproductive drive (the reproductive-hormone load that also fuels mammary tumors)^[1] seems to come with it. Our roof rats are tame in temperament but still close to their wild-type health, so they may simply not carry that built-in risk. That is our own observation and a hypothesis, not settled science, and it is exactly the kind of question we would love to see studied.

There is probably a second half to this. Pet rats also tend to run overweight, and excess body fat is itself linked to higher rates of many cancers^[2], so a leaner animal is at lower risk on that axis too. Our roof rats stay lean and were never bred for fast, heavy breeding, which makes them a useful natural control for the tumor and obesity biology of the fancy rat: lean, never selected for fecundity, and close to wild-type health. We lay out that hypothesis, and the test that would settle it, on our open research questions hub.

My rat has a lump. Is it a tumor?

Maybe. A lump that came up fast, feels warm, and may have a scab is more likely an abscess;^[4] one that grew slowly over weeks and is soft and slides under the skin is more likely a tumor, usually a benign mammary lump.^[5] Either way have an exotic vet look, and remember that spaying a young female prevents most of these. Full guide to tumors and lumps.

My rat’s head is tilted to one side. What is wrong?

A tilted head, circling, or falling is a balance problem. In most rats it is an inner-ear infection, and in an older rat it can be a pituitary tumor.^[6] See a vet quickly, because the sooner an ear infection is treated the more head tilt comes back. Full guide to head tilt and balance.

My rat is scratching with scabs over its shoulders. What is it?

Scabs and itching across the shoulders and neck are usually mites or lice, and sometimes ringworm. They are treatable with ivermectin or selamectin from a vet, and you treat every rat in the cage plus a good clean.^[7] Full guide to skin, itching, and parasites.

My older rat’s back legs are getting weak. Why?

In an older rat, slowly weakening or dragging back legs is usually age-related nerve degeneration. It is not painful and is not reversible, but keeping the rat lean and the cage low and easy to get around makes a real difference to quality of life. A vet should rule out other causes first. Full guide to aging and hind-leg weakness.

My rat is drooling or dropping food. Could it be teeth?

Yes. Drooling, a wet chin, dropping food, or losing weight while still interested in food all point to overgrown teeth. A vet grinds them down with a burr; never let anyone clip them, which can fracture the tooth.^[8] Weigh the rat, because weight loss is the earliest sign. Full guide to teeth and mouth.

My rat’s belly is hard and bloated. Is it an emergency?

Yes. A rapidly swelling, drum-tight belly, or no stool passed in 12 hours, is a go-now emergency, because a rat cannot burp or vomit to relieve trapped gas.^[3] Head to a vet straight away, especially if the rat is also breathing with an open mouth. Full guide to digestion problems.

What supplements actually help an aging rat?

The best-supported in rats are acetyl-L-carnitine,^[9] alpha-lipoic acid,^[10] methylcobalamin (B12),^[11] omega-3, and betaine; ergothioneine is promising; CBD can help but needs real caution. None of these replace a vet, and a few can thin the blood, so tell your vet what you give. What the evidence shows, with the cautions.

How do I find a vet who treats rats?

Look for an exotics vet, sometimes listed as “exotic companion mammal,” rather than a dog-and-cat-only clinic. The AEMV and ABVP directories list them by area, and it is worth calling ahead to confirm they see rats and asking if they have treated them recently. Our find-a-rat-vet tool builds the right searches for your area, lists the directories, and lets you add a good vet you know.

Can ergothioneine help protect an aging rat’s kidneys?

Possibly, and it is one of the better reasons to care about it. Ergothioneine concentrates in the exact part of the kidney that wears out with age, and in rodents it protects that tissue and slows the slide from kidney injury into permanent kidney disease.^[12] There is a hard catch: kidney disease itself lowers the amount of ergothioneine an animal carries, measured in mice and in people rather than in rats, so the time to keep the diet rich in it is before there is a problem, not after.^[13] It is not a cure and will not reverse kidney failure, so a rat that is losing weight or drinking and peeing more still needs a vet. The mechanism is laid out on our ergothioneine science page.

Is ergothioneine safe to give a rat?

Yes, it is one of the safest things you can add. It is approved as a food ingredient in the EU and recognized as safe in the US, and in rat studies the no-harm dose is hundreds of times higher than any amount you would feed. The one honest caveat is cancer: because tumors also use antioxidants, if a rat already has a tumor it is worth asking a vet before loading up. For a healthy rat, a little mushroom in the diet carries essentially no risk. The safety evidence is on our ergothioneine science page.