By Melissa Oglesbee, B.S., A.A.S., former RVT
Bloodwork. Why is it important? Why does my veterinarian ask me to do it every year when my pet is obviously healthy? Why does my sick pet need to be monitored in this way? Is bloodwork on my perfectly healthy pet really necessary before anesthesia? Why do you need to use bloodwork to monitor certain medications? And why do dogs need a heartworm test every year since my pet gets a preventive every month without fail?
These are all very valid questions. Bloodwork may seem to be unnecessary and just an added cost to a pet owner, but it can provide loads of valuable information to the medical staff for both sick and well pets.
For pets without any symptoms, this is super important, which is why your veterinarian recommends a wellness panel every year. There are several diseases which do not show any symptoms until they are very advanced. But bloodwork can show your veterinarian very early stages, and thus, they can sometimes address these issues before they have serious complications. For example, diseased kidneys do not produce any clinical symptoms in the beginning; a kidney can function at 25% capacity, so you may never know the level of deterioration. However, bloodwork can reveal early kidney disease, when your veterinarian can often recommend things to slow the progression. But once a pet is showing symptoms, the disease is typically advanced, and your veterinarian may only be able to try managing the symptoms. I use kidney disease as an example, but bloodwork can also reveal liver issues, blood disorders, and even some cancers, long before your pet becomes symptomatic. These conditions can and do affect pets of all ages.
If your pet is sick, bloodwork is also important. Not only does bloodwork help in diagnosing a condition, but it can also tell your veterinarian if a treatment is working. This can not only save you time and money but, more importantly, it spares your pet from treatments that are not effective, so your veterinarian knows to try something else. In addition to monitoring treatment, it can also direct treatment. For example, if an animal has been hit by a car, a prominent symptom is that the gums are pale. But is this from anemia (blood loss) or shock? The treatments are very different, but bloodwork can tell us where to go. This is really important because pale gums mean the body is not circulating oxygen very well, so time is of the essence. Your veterinarian does not want to waste time addressing anemia if shock is really the cause of poor circulation.
Prior to any anesthetic procedure, bloodwork is also usually required. Why? Because anesthesia on a healthy animal is a relatively low-risk procedure. But if there are any hidden health problems, then the risk goes up. This doesn’t necessarily mean that a procedure cannot be done. But your veterinarian will know to alter the anesthetic protocol to lower the risk for your pet. This is essential for your pet’s safety. As I mentioned previously, there are several diseases that have no symptoms in the early stages. But bloodwork can reveal hidden conditions that the medical staff can usually make accommodations for. For example, they may increase the fluid rate for an animal with kidney disease. Bloodwork can help your veterinarian tailor an anesthetic protocol in a way that’s safest for your pet.
Bloodwork can also tell your veterinarian if certain medications are safe, or if the current dosage is effective for your pet. NSAIDs—non-steroidal anti-inflammatory drugs, such as Deramaxx—are generally safe, but their use can affect the kidneys, liver, and GI tract in general (dogs and cats are much more sensitive to this class of drugs than humans, which is why you should never give human pain relievers to pets), so periodic bloodwork is needed for a pet that is on an NSAID long-term. Also, these drugs should generally not be given to a pet that has known kidney or liver issues, which can be revealed by bloodwork, even if your pet is asymptomatic. Bloodwork can also tell your veterinarian if drugs like phenobarbital, thyroid medication, or insulin are at the correct doses.
Finally, why do you need a heartworm test every year or before starting heartworm prevention? Well, giving a dog heartworm prevention when he/she has heartworms can actually be dangerous. Heartworm prevention only kills the developing juvenile heartworms, not the adults. Adult worms create microfilariae (essentially, baby heartworms), which can react with any preventives, potentially causing a life-threatening reaction. And even if you’re very faithful about giving a preventive every month, it’s always possible that your dog spit out or vomited up the pill. So it’s very possible that your dog can be unprotected unbeknownst to you. Again, heartworm disease is one of those conditions that if caught early, is much easier and safer to treat. However, there are usually no symptoms in the early stages, and infection this early can only be detected with a blood test. To learn more about what happens when your dog gets heartworms, click here.
Bloodwork may seem superfluous, but it can catch disease in its early stages, monitor and direct treatment for sick pets, give your veterinarian information that allows him/her to adjust anesthesia, let them know if it’s safe to give a drug, or if they are giving your pet the therapeutic dose of a drug, and detect heartworms in asymptomatic pets. Our pets cannot tell us what is going on inside, but bloodwork can!