As your gerbils get older, they may have some special needs related to aging. Gerbils usually live to be about three years old. Some gerbils don't make it that long, while others live to be around 4 years old. You can expect, though, that you will have about three years with your pet gerbil.
When your gerbil turns about 2 1/2 years old, it's time to keep an eye open for developing problems. You can't make your gerbils live forever, but you can ensure that they live the longest, happiest life possible. Read on to learn some of the special considerations for older gerbils.
Subtle changes. Usually, a gerbil's coat will get lighter as she or he ages. This is nothing to be concerned about and is a normal part of the aging process. A nutmeg gerbil who was once very dark may start to show more of a golden color. A Siamese gerbil may have lighter points than when he was younger. Many times, this lightening of the coat is the only sign that your gerbil is in his or her senior years.
If this is the case, your pet may never have any major health issues but may instead just gradually slow down as he or she gets older.
Other times, it's more obvious that a gerbil is winding down. A gerbil who is over two years old may have more squinty eyes, spend more time sleeping, or run in the wheel at a more leisurely pace.
Teeth. If your gerbil is losing weight suddenly, hand him a sunflower seed and watch carefully to see if he can eat it. If he has trouble, examine his teeth to see if they are overgrown or if they are different lengths. Elderly gerbils' teeth are more prone to breakage that younger gerbils' teeth. Also, because older gerbils spend more time sleeping and less time chewing on wooden blocks and cardboard tubes, their teeth may not stay trimmed to the proper length. Make sure you give your older gerbil plenty of wood and cardboard to chew on, but if there seem to be problems with your gerbil's teeth despite your best efforts, go to the vet. A vet can trim a gerbil's teeth so that he can once again eat solid food. Just remember that overgrown teeth, not illness, is the most common cause of weight loss in older gerbils.
Tumors & cysts. Although any age of gerbil can develop a tumor, cyst, or other mass, these are usually found in older gerbils.
Males are more likely than females to get scent gland tumors. Your gerbil's scent gland is the yellowish patch of bare skin right in the middle of its belly, where the fur parts slightly. If the scent gland has a raised, red bump, you should have your vet examine it. Surgeries to remove scent gland tumors are very simple and have a high success rate. There is some risk involved in using anesthesia on an older gerbil, though, so you should weigh the pros and cons of surgery with your vet.
Female gerbils are more prone to abdominal tumors and ovarian cysts. You'll notice these when your older female gerbil starts to look pear- or bell-shaped. Again, a trip to the vet is recommended. Surgery for internal growths such as these is not as simple as scent-gland removal surgery, so your vet may not be able to remove the cyst or tumor. However, your vet can often suggest a treatment that will make your gerbil's remaining time more comfortable. Also, at your request, if your gerbil is suffering and no longer enjoying life, your vet can perform a humane procedure to put your pet to sleep.
Strokes. Older gerbils may have strokes. 
You can usually tell that a gerbil has had a stroke when he or she has suddenly lost the use of a couple of limbs or when half the face is droopy, as seen in the photo to the left.
If your gerbil suffers a stroke, there is little to do except provide a good environment for recovery. First, make sure that your gerbil can still get to the water bottle. Lower it if you need to. If your gerbil can't feed itself or drink, you can offer some sugar-free organic baby food (apple is a popular flavor with gerbils) on a spoon and let your gerbil lick the baby food up. Your gerbil may also like some lukewarm, cooked oatmeal. You can use an eyedropper to give your gerbil water.
Beyond that, just cover one half of the tank with a towel so that your gerbil has a dark area to rest. Keep noise and traffic in the room to a minimum. The less stressed your gerbil is, the faster he or she will recover.
Usually, gerbils recover from strokes on their own. Occasionally, though, a gerbil may have a series of progressively worse strokes. In most cases, though, there will be a full recovery.
Sudden weight changes. Something everyone with an older gerbil should pay attention to is sudden weight gain or weight loss. A sudden loss in weight may be a sign of tooth problems, but it could also signal kidney failure or other serious problems. Sudden weight gain may be related to tumors or heart failure.
If you keep an eye on your older gerbils' health, you can avoid many common problems, and you can help your gerbil to live the longest and fullest life possible.