Weight loss is very common in guinea pigs and is not a cause for panic. But when you notice your guinea pig losing weight, you should monitor the situation very carefully to make sure everything's going right. Naturally, this means you should regularly weigh your pig (twice a week is advisable) and look for a significant change in weight.
How much is a "significant" change in weight?
A guinea pig's weight will normally differ by a few grams every time you weigh. This is because of hydration, food (or lack thereof) etc. So a difference of up to 35 grams (1.2 ounces) per week shouldn't be too much of a concern. However, if the weight drop is above this level, you should certainly take notice. A drop of over 85 grams (3 ounces) almost certainly means an emergency and you should rush to the vet right away.
What to do if you notice a weight loss.
If you notice a significant weight loss of over 2 ounces, you should check to see if your pig has been eating and drinking properly. Most of the time, insufficient nutrition is the culprit. Don't be fooled simply by seeing empty food bowls, though, because guinea pigs sometimes stow away their food instead of eating it. So even if all the food has disappeared, the pig might not have eaten it all.
If you find that your pig won't eat properly, you can quickly try changing his or her diet. Buy a different brand of guinea pig food, spice up the menu with different fruits, vegetables etc. If it still doesn't work, then there's a problem and you need to see a vet. Until you see one, you should make sure the pig is decently fed even if it means force-feeding him or her. Force-feeding should be done very carefully with the help of a clean syringe.
What is the average weight of a guinea pig?
Sometimes, you may notice that your pig loses weight within the safe range but the weight keeps dropping week after week. Such consistent loss is alright as long as the cavy doesn't gradually go too light. Obviously, every guinea pig is different and has its own natural weight but if your pig is an adult female, her weight shouldn't normally drop below 1.5 lb. (24 ounces) and if male, his weight should be no less than 2 lb (32 ounces). The only exception to this rule is if your piggy is of an unusually small frame.
A number of diseases can cause your guinea pig to lose weight fast. The most common of these are malocclusion and scurvy, either of which may be diagnosed by your veterinarian. Sometimes, problems in the pig's teeth can also hurt the pig while eating, discouraging him from eating anything; this can also contribute to weight loss.