Doctors often use the complete medical history of the patient to diagnose gout. This is a vital source of information. Family history of gout, sudden attacks of arthritis in one or more joints, tendinitis or sprains which happen without an injury, and the usage of certain medications like aspirin and diuretics increase the probability of gout in a person. Other critical factors that are examined are recent diets; recent infections in the kidneys, skin, bladder or lungs; lifestyle conditions like alcohol consumption and other medical conditions.

Since a gout attack is often accompanied by fever, taking the temperature when gout is suspected is a compulsory diagnostic tool. The skin over the affected joint will be warm, red or swollen or all of three will occur together in case of gout. Feeling the joints to assess the pain levels and examining the skin for any cuts and infections are also done during the physical exam. The affected joint is moved and tested for its range of motion. In case of gout, the range will be seriously hampered.

It may seem strange that treatment has been listed as a diagnostic test. But it is often the most effective way to diagnose gout. Since the symptoms of gout are similar to a host of other conditions, the best way to uncover the truth would be to start treating for gout. If the medication and treatment helps, that is sure proof of gout being the problem. And the problem is treated along with the diagnosis! Then, the necessary steps to prevent future attacks can be taken. Of course, treatment should be begun only after the history and physical examination confirm or at least point towards gout.

Gout is caused by the deposits of uric acid salt crystals in the connective tissues. These will be present in the blood as well. So the uric acid levels in the blood are checked. This, however, is misleading at times because there are many recorded cases of people who have high uric acid levels in the blood but do not suffer from gout. Also, about 30 percent of the patients have normal uric acid levels in the blood when they are suffering from a severe bout of gout. The test, however, is useful to check whether the gout medication is working or not. It also helps to determine the probability of stones forming in the kidneys due to the uric acid concentration. 

Uric acid builds up in the joints and results in lumps known as tophi. Since the kidneys are involved in filtration of blood and removal of uric acid via the urine, they can often get affected with the formation of stones. Thus, measuring the concentration of uric acid in the urine sample is useful. This diagnostic works well along with the blood test. If the blood samples show high uric acid concentrations while the urine levels of the same are low, this means that the urate crystals are getting deposited within the body and not being excreted out.

This procedure is also known as the joint fluid test or the joint aspiration. This is a very reliable method of diagnosis and it almost always predicts the presence or absence of gout with 100 percent certainty. Using a syringe with a needle, the synovial fluid from the affected joint is drawn and a sample is made. This synovial fluid is the analysed thoroughly under a microscope. If the analysis reveals monosodium urate (MSU) crystals, then this is a sure indicator of gout.

Taking an X-ray of the joints in question, especially if they happen to be the extremities like the toes and fingers, is another helpful diagnostic tool. X-ray films of tips of the affected joints will often show signs of gout. The tophi crystals are clearly seen and they appear as erosions on the bone. These erosions are different from those of rheumatoid arthritis. In the case of gout, the erosions are further from the margin of the joints. Thus, reading the X-ray films helps to determine whether one is affected with gout or not.