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Pet Rats/Rat seems very thin


My rat is about a year and a half old, and a male. He has plenty of energy, he's definitely eating, and he seems to have no health problems other than he seems to be getting kind of thin. This happened to my other rat, and he passed away. I'm really afraid that the same will happen to Silferno (this rat), especially because I am attached to him. He eats three lab blocks a day, which seems to be the recommended. Does he need more food? Am I not feeding him enough? Or is there something else going on?

Hi Jenny,
There is probably something else going on. Are you sure his breathing isn't a little abnormal? Maybe a little harder or faster than normal?  Respiratory disease is very common in rats, and a mild case can cause them to lose weight. It would be a good idea for you to put him on doxycycline as a treatment for mycoplasma. All pet rats have myco, and I put my older rats on doxy permanently as a preventative. Depending on their health history, I might do this as young as 1 1/2. See the info below.

You can get one hundred 100 mg doxycycline capsules mail order for $17.99 from  Click on their eShop page.

To mix doxycycline capsules:

In a film canister, put 12 cc (12 ml) of liquid such as slightly diluted Hershey’s strawberry syrup.  Open and dump in the contents of one 100 mg doxycycline capsule.  Stir well.  The amount for the typical dose of 2.5 mg/lb is 0.3 ml/lb (0.3 cc or 30 units on an insulin syringe) twice a day.  For 5 mg/lb give twice that.  To use an insulin syringe for oral dosing, break off the whole needle assembly.  Be sure to refrigerate the mixture.

If you don’t have the proper syringes for dosing, dump the capsule out on small plate and divide the powder into 40 equal piles.  (Divide in half, then in half again, etc.)  Each pile is a dose and can be scraped into soft food.

You can also order doxycycline, from Jedds Pigeon Supplies, and if you do you might consider also getting Baytril (enrofloxacin) which is also a good antibiotic for treating mycoplasma in rats if the doxycycline doesn’t work.  When calling, ask for Greg. You can also order it on their website at If ordering online, order item #5002.  It won’t say it’s Baytril, as they keep it quiet. It is only legal to buy Baytril over the counter for birds.

You can buy 100 ml of 10% oral generic Baytril from Jedd's Pigeon Supply for $40 plus shipping.  The dose for a 1-lb rat is 0.1 ml, which means that 100 ml is 1000 rat doses!  Very economical.  You need to give it twice a day.  Do not refrigerate the 10% Baytril. I've had the best luck giving it in in 4-6 ml of a product such as strawberry Ensure, Boost or soy baby formula in a baby food jar lid, or in 1/8 teaspoon of the soy baby formula powder, making a paste.  It helps if you put the baby food jar lid on a small magnet to help keep your rat from tipping it over.

Another very good antibiotic to have on hand for rats is amoxicillin.  This is good for secondary infections which can hit them hard and fast and sometimes cause death within 24 hours, so having it on hand means you can start them on it immediately and possibly save their life. I always recommend trying amoxicillin first when a rat first shows signs of being sick, and if it doesn’t work, then you can try doxycycline.

You can also get 100 250 mg amoxicillin capsules from Be sure to order CAPSULES.   Amoxicillin is good for all rat owners to have on hand because it is the best treatment for secondary infections which can come on very quickly and severely, killing rats within 12-24 hours without proper treatment.

For dosing you need to know about how much your rat weighs.  The dose is 10 mg/lb twice a day but you can safely go as high as 50 mg/lb.  In most cases (check the package) each amoxicillin capsule contains 250 mg, which is 25  1-lb doses.  

If you have access to small syringes for measuring you can mix the amoxicillin in a liquid.  Dump one capsule out on a plate and see if it is granules or powder.  If granules, grind them to a powder with the back of a spoon. Amoxicillin doesn't taste too bad to most rats, so I suggest making the liquid dose 0.3 ml (30 units on an insulin syringe) per lb.  (Note:  1 cc = 1 ml = 100 units.)  Multiply the volume of the dose by the number of doses in the capsule:  0.3 ml times 25 doses equals 7.5 ml.  So you mix a capsule in 7.5 ml of liquid such as Hawaiian punch concentrate or Hersey's strawberry syrup.  A film canister is about the right size to put it in.  Keep in the refrigerator.  If your rat won't take this voluntarily, you can make the dose 0.1 ml which is too small for them to spit out.  0.1 ml X 25 = 2.5 ml so you mix one capsule with 2.5 ml of tasty liquid.

If you don’t have small syringes, you can mix it in food.  Dump a capsule out on a plate.  If it is granular, grind it to a powder.  Divide the powder in half, and half again, etc.  Until you have 24 piles. Since it’s hard to divide it more than this, you can give the 1-lb dose to rats who weigh less than a pound.   It’s better to give too much than not enough.  Scrape a pile into a little bit of food such as baby food, mashed avocado, etc.  

Give the dose twice a day.  If it's going to work the symptoms should improve within 2-3 days.  If it does work you need to continue the treatment for at least 2-3 weeks.  If it doesn’t work then you need to try a different treatment.  

If this treatment is going to help you should see improvement within 2-3 days.  If the symptoms are all gone within 3 days you should continue the treatment for 3 weeks.  If it takes longer for all the symptoms to go away, give it for 4-8 weeks and maybe longer.  The longer it takes for all the symptoms to go away, the longer you should continue the treatment.  If the symptoms stop improving, or if the amoxicillin doesn't help at all, you will need to try something else.

You will find more info about treating respiratory infections on my website at on the Rat Info page.  I also highly recommend you order my Rat Health Care booklet.  It is only $7 plus $2 shipping (CA residents add 58 cents tax.)  The address is Rat Fan Club, 857 Lindo Lane, Chico CA 95973.

Concerning amoxicillin and veterininarians:  Many vets don’t want to use amoxicillin on rats.  This is probably because in vet school they learn that amoxicillin can’t be used in guinea pigs, rabbits or hamsters (because it kills the good bacteria in their intestines), and they probably generalize this to rats and mice.  However, rats and mice usually tolerate amoxicillin quite well.  In my experience only a very small percentage of them will get diarrhea from it, and this is not life-threatening; it will usually clear up with a probiotic, or the amoxicillin can be stopped.

Here are some references for using amoxicillin in rats for your vet to check if they are reluctant to prescribe amoxicillin:

Exotic Animal Formulary, Third Edition, James W. Carpenter, MS, DVM editor, Elsevier Saunders Publishing
Page 377, Antimicrobial and antifungal agents used in rodents.
Ampicillin for mice and rats: dosage 20-50 mg/kg PO, SC, IM q12h
(Note: ampicillin and amoxicillin have essentially the same adverse reactions and effectiveness, so they can be used interchangeably)

ViN (Veterinary Information Network, Inc.) Website

Thomas Donnelly, BVSc on 02/05/2006  “Amoxicillin is safe to give rats.”

Johanna Briscoe, VMD, on 07/08/2004  “I have used Clavamox liquid in a rat and it worked beautifully on an abscess that I thought may have been from a bite….  Clavamox dose same as in other mammals—13.75 mg/kg PO BID.”
(Note: Clavamox is the brand name for a mixture of amoxicillin and clavulanic acid.)

Elizabeth Mitchell on 06/01/2007  “I have used Clavamox a few times in rats without problems, although I am always very careful to warn owners to watch for diarrhea.”

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Debbie Ducommun


I can answer any questions about pet rats, but you will probably be able find answers to simple questions more quickly on my website at If you have a life-threatening emergency you can try calling me at 530-899-0605. I am not usually on the computer on the weekend.


I have been "The Rat Lady" since 1985 and am recognized as one of the world's experts on pet rats. I have 3 published books and already answer lots of questions about rats daily.

President of Rat Assistance & Teaching Society

I am a monthly columnist for Pet Business magazine, and my writing has appeared in other magazines. I have 3 published books.

BA in Animal Behavior

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