The primary blood test for gout is a serum uric acid test, which measures how much uric acid is circulating in your blood. A level above 6.8 mg/dL is the point at which uric acid crystals can form in joints, though most doctors use 7 mg/dL as the upper threshold for men and 6 mg/dL for women. But uric acid alone doesn’t confirm or rule out gout, so doctors typically order several blood tests together to build a complete picture.
The Serum Uric Acid Test
This is the test most people think of when they hear “blood test for gout,” and it’s a straightforward blood draw with no fasting required. The lab measures the concentration of uric acid in your blood, reported in milligrams per deciliter (mg/dL). High levels suggest your body is either producing too much uric acid or not excreting enough of it through the kidneys.
Here’s the catch: a single uric acid reading can be misleading, especially during a flare. A study in The Journal of Rheumatology found that 14% of patients had completely normal uric acid levels (at or below 6 mg/dL) during an active gout attack. About a third had levels at or below 8 mg/dL. Uric acid can temporarily drop during a flare because the inflammatory process pulls it into the joint. So if your result comes back normal while your toe is red and swollen, that doesn’t mean you’re in the clear. Your doctor will likely retest once the flare has resolved to get a more accurate baseline.
On the flip side, plenty of people walk around with elevated uric acid and never develop gout. High uric acid is necessary for gout but not sufficient on its own.
Inflammatory Markers: CRP and ESR
During a suspected gout flare, doctors often check two markers of inflammation alongside uric acid. C-reactive protein (CRP) measures a protein your liver produces when there’s inflammation anywhere in the body. Erythrocyte sedimentation rate (ESR) measures how quickly red blood cells settle to the bottom of a test tube, which happens faster when inflammation is present.
Neither CRP nor ESR can diagnose gout specifically. What they do is help distinguish gout from something more dangerous: a joint infection. A CRP level under 100 mg/L, combined with other findings, points more toward gout. Levels that are dramatically higher, along with a very high white blood cell count in the joint fluid, raise suspicion for septic arthritis, which is a medical emergency. Fever above 100.4°F and elevated white blood cells on a standard blood count can accompany both conditions, which is why these markers are interpreted together rather than in isolation.
Kidney Function Tests
Because the kidneys are responsible for filtering about 70% of the uric acid your body produces, impaired kidney function is the most common reason uric acid builds up in the blood. Doctors frequently order kidney function tests alongside uric acid, particularly if gout is confirmed or suspected.
Two tests matter here. The first is a blood test that estimates your glomerular filtration rate (GFR), which tells you how efficiently your kidneys are filtering waste. The second is a urine test called the albumin-to-creatinine ratio (ACR), which checks whether protein is leaking into your urine, a sign of kidney damage. The National Kidney Foundation recommends that anyone with gout get screened for kidney disease, because the same mechanism that causes crystal buildup in your joints can also damage your kidneys over time.
A Complete Blood Count
A complete blood count (CBC) is often part of the initial workup. It measures your white blood cells, red blood cells, and platelets. During a gout flare, white blood cells are frequently elevated as your immune system attacks the uric acid crystals in the joint. This test is most useful for ruling out infection or other conditions that mimic gout, rather than for confirming gout itself.
Why Blood Tests Alone Aren’t Enough
Blood tests provide supporting evidence, but the gold standard for diagnosing gout is actually joint fluid analysis. A doctor uses a needle to draw fluid from the affected joint and examines it under a polarized microscope. If monosodium urate crystals are visible, that’s a definitive diagnosis. This procedure also rules out infection by checking the white blood cell count in the fluid itself: counts under 10,000 favor gout, while counts above 50,000 raise serious concern for a bacterial joint infection.
Not every patient needs a joint aspiration. If you have a classic presentation (sudden, severe pain in the big toe with elevated uric acid and inflammatory markers), many doctors will diagnose gout based on the clinical picture and blood work alone. Joint aspiration becomes more important when the diagnosis is uncertain, the joint involved is unusual for gout, or infection needs to be ruled out.
What Your Uric Acid Target Looks Like
If you’ve been diagnosed with gout and started on medication to lower uric acid, your doctor will use repeat blood tests to track whether your levels are reaching the target. The widely accepted goal is to get serum uric acid below 6 mg/dL (360 μmol/L). For patients who have visible deposits of uric acid under the skin, called tophi, the target is more aggressive: below 5 mg/dL (300 μmol/L). Staying below these thresholds allows existing crystals in the joints to gradually dissolve, which reduces the frequency and severity of flares over time.
This is a treat-to-target approach, meaning your medication dose gets adjusted based on your blood test results, similar to how blood pressure medication is titrated. You’ll typically get uric acid levels checked every few weeks during dose adjustments, then every few months once you’ve hit your target.
Timing Your Blood Test
If you’re getting tested for the first time during a painful flare, understand that the result may not reflect your true baseline. A normal reading during a flare doesn’t rule out gout, and a very high reading during a flare might be somewhat lower once the inflammation settles. For the most accurate picture of your usual uric acid level, testing works best when you haven’t had a flare for at least two to four weeks.
Certain medications can also skew results. Diuretics (water pills) commonly prescribed for blood pressure tend to raise uric acid. Low-dose aspirin has the same effect. If you’re taking either, mention it before your test so your doctor can interpret the number in context.