Hello and welcome. My name is ***** ***** I'm a biologist with a special interest in small animal health. I'm sorry to hear that Bubbles is having a problem.
First of all, there's no reason you can't give your hamster a little cranberry juice. However, there are other causes for blood in the urine besides a urinary tract infection (UTI). A urinary tract infection often accompanies bladder stones, especially in an older hamster like Bubbles. If she does have stones, an antibiotic will clear up the accompanying infection, but the stones will remain. In that case, the hamster would continue to urinate blood and feel pain when he pees. X-rays would probably detect any stones, but removing them is not easy in a hamster.
The other concern is that there is a fungal infection, aspergillis, that causes blood in the urine. But, it often has other symptoms, too, such as breathing problems and diarrhea. The fungus grows on urine as a black residue. If you don't allow wet litter to remain in the cage, this fungus is unlikely, but if it is present, it will only respond to antifungal medication. There's more information on this site:
Because your hamster doesn't have the other symptoms, I'm more concerned that she may have stones than aspergillis.
The other possibility is that this blood was a one time thing. You may choose to have a vet examine her, or you can try the cranberry juice and keep an eye on her. If she cries when she urinates, strains to urinate, passes more blood, or become lethargic or stops eating, then it would certianly be best to take her to your vet.
If you have more questions, just let me know. I hope Bubbles will be fine.
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