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Pet Rats/Grunting rat


My rat is a little over a year and a half old; two days before Thanksgiving he started making these odd grunting and squeaking sounds.  I put him on amox right away in case it was a secondary infection.  The next afternoon I brought them all with me up to my parents house for the holiday.  That night the sounds had significantly decreased and were gone whenever I checked on him on Thanksgiving day.  Assuming it must have been a secondary infection starting I decided to just continue the amox treatment but I noticed yesterday night the sounds reappearing and the are back a lot more tonight.  There is no change in energy level or temperament and he is eating a drinking well.  If it wasn't for the sounds I wouldn't suspect anything to be wrong

Is there a chance that my house is the problem?  I live in the upper midwest and it recently started getting a lot colder here.  My house is a lot older than my parents house.  It sits colder and is probably a lot drier.  I put a space heater in with them as well as a big bowl of water to help with the humidity, but I could grab a humidifier if you think that's the problem?  There were no sounds when he was at my parents house but they started up again here.  Maybe it's the environment?

Hi Marissa,
Good job starting him on the amoxi!  It seems unlikely that the cause would be your house. It could be he has both a secondary infection and myco, so I recommend continuing the amoxi and adding doxycycline. See the info below.

You can order doxycycline capsules here:
If you would prefer a liquid they also have Doxysyrup or Doxyvet Liquid. Most people will want to order Doxysyrup, which is 10 mg/ml. The normal dose is 0.25 ml/lb twice a day. If necessary you can give twice this.

If you own a lot of rats, the most economical choice is Doxyvet Liquid, which is 50 mg/ml. The normal dose is 0.05 ml/lb twice a day. If necessary you can give twice this. I have heard from several rat owners that this liquid is not as palatable as the Doxysyrup, but it can be diluted with yummier liquid or mixed with food. If you mix 1 ml of the Doxyvet with 5 ml of flavoring, and then the dose is 0.3 ml/lb twice a day. Depending on the flavoring you use, the mixture should probably be refrigerated.

You also want to buy a few 1 cc syringes for dosing (take off the needle and throw it away), and you can buy syringes at most pharmacies. A 12 cc or 3 cc syringe is also helpful for measuring the flavoring liquid.

Jedd’s Pigeon Supplies is 800-659-5928. You can also order on their website at Go to their shopping cart to search for items.

You can also order 100 mg capsules of doxycycline at a cheaper price on eBay at  This company is in Singapore, so expect shipping to take 2-3 weeks.

For 100 mg doxy capsules, mix one capsule with 12 ml of flavoring (slightly diluted strawberry syrup works good) and then the dose is 0.3 ml/lb twice a day. Store in the refrigerator and stir before taking out a dose.

You need to give the doxy for at least 6 weeks, and for older rats, I recommend them on it for the rest of their life to keep the mycoplasma under control.

If the doxy doesn’t work, then you should try amoxicillin (see below). If that doesn’t work, you can try Baytril (enrofloxacin), which is also a good antibiotic for treating mycoplasma in rats if the doxycycline doesn’t work.  

You can buy 100 ml of 10% oral generic Baytril (enrofloxacin is the generic name but it can be called enroxil or enrofloxacine) from pigeon supply companies for birds. 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 Baytril!

I’ve had the best luck giving Baytril in 4-6 ml of a product such as strawberry Ensure or Boost 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.  

You can order it from

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.  

You can mix the amoxicillin in a liquid such as slightly diluted Hersey's strawberry syrup, Ensure, apple juice, milk, etc. A short pill bottle is about the right size to mix it in. . Amoxicillin does not dissolve but forms a suspension. The powder will sink to the bottom, so before taking out a dose, you need to stir the mixture with the syringe extremely well, being sure to scrape up all the powder off the bottom so it is in suspension.

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.  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.   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.

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.”

Blackwell’s Five-Minute Veterinary Consult: Small Mammals, Second Edition, Barbara L. Oblesbee. 2011 John Wiley & Sons, Inc. page 588, “amoxicillin/clavulanic acid (12.5-15 mg/kg PO q12h) may also be used.”

(Note: Clavamox is the brand name for a mixture of amoxicillin and clavulanic acid.)

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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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