Definition: A uric acid blood test measures the amount of uric acid, also called serum urate, in the bloodstream.
What is uric acid?
Uric acid is a normal waste product produced when the body breaks down chemicals called purines. MedlinePlus says purines come from natural cell turnover and are also present in many foods and drinks. Most uric acid dissolves in blood and is filtered out by the kidneys into urine. If the body makes too much uric acid or does not remove enough, blood levels can rise.
In UK clinical language, you will often see serum urate rather than uric acid. They are closely related terms and, in everyday lab-result use, usually refer to the same measurement target. NICE uses the term serum urate in its gout guideline.
Why is a uric acid blood test done?
MedlinePlus says a uric acid blood test may be used to help diagnose gout, usually together with synovial fluid assessment, and to monitor people having cancer chemotherapy or certain other cancer treatments because rapid cell breakdown can release extra purines into blood. The test can also be relevant for kidney stones and kidney disease, especially when paired with urine testing.
NICE adds a very useful UK angle. In people with symptoms and signs of gout, it recommends measuring serum urate to help confirm the clinical diagnosis, using 360 micromol/L or more as a supportive level, while also advising repeat testing at least 2 weeks after a flare settles if serum urate is below that level during a flare and gout is still strongly suspected.
High uric acid does not automatically mean gout
This is the main page guardrail. MedlinePlus says high uric acid can be related to gout, kidney disease, blood cancers, certain cancer treatments, alcohol use disorder, and preeclampsia. It also says many people have high uric acid without having health problems.
That matters because the test is often misunderstood. A high uric acid result may support gout in the right clinical setting, but it is not enough by itself to make the diagnosis. NICE specifically says that if gout remains uncertain, joint aspiration and microscopy of synovial fluid should be considered, and imaging may be used if needed.
What causes high uric acid?
MedlinePlus says high uric acid in blood may happen if the body makes too much uric acid, if the kidneys cannot remove it efficiently, or if a person consumes high-purine foods and drinks such as organ meats, certain seafood, alcohol, and products high in fructose corn syrup. It also lists gout, kidney disease, leukaemia, multiple myeloma, metastatic cancer, cancer-treatment effects, alcohol use disorder, and preeclampsia among possible linked conditions. Dehydration, excessive exercise, hypothyroidism, obesity, and some medicines can also contribute.
What causes low uric acid?
Low uric acid is less commonly the main issue. MedlinePlus says low levels in blood are uncommon and usually do not cause health problems. Possible associations include low-purine diet, some medicines, SIADH, Fanconi syndrome, HIV infection, and some hereditary metabolic conditions. For most patients, low uric acid deserves coverage but not alarm.
Uric acid interpretation table
| Result | UK (serum urate) | US (uric acid) | General meaning |
|---|---|---|---|
| Low | Below ~180 µmol/L | Below ~3.0 mg/dL | Uncommon; may reflect diet, medicines, or rare metabolic conditions |
| Normal | ~180–420 µmol/L | ~3.0–7.0 mg/dL | Within typical reference range; varies by lab and sex |
| Raised | Above ~360 µmol/L (NICE gout threshold) | Above ~6.0 mg/dL | May support gout diagnosis in right clinical context; not diagnostic alone |
| High | Above ~480 µmol/L | Above ~8.0 mg/dL | Associated with higher gout risk, kidney stones; clinical review needed |
UK uses µmol/L (serum urate); US uses mg/dL (uric acid). Ranges vary by laboratory and sex. Always use your own lab’s reference interval.
This table is a general educational guide. Reference ranges vary by laboratory, units, sex, age, and clinical context. NICE thresholds for suspected gout are a clinical guideline tool and should not replace local lab reporting.
| Uric acid pattern | What it may suggest | Main reminder |
|---|---|---|
| High uric acid | May reflect reduced kidney clearance, increased purine turnover, diet, medicines, or gout-related context | High uric acid alone does not prove gout |
| Normal uric acid | Blood urate is within the local interval | During a gout flare, a normal or lower value does not always exclude gout |
| Low uric acid | Usually less clinically significant | Often interpreted with broader clinical context rather than as a stand-alone problem |
Uric acid and gout
NICE says to measure serum urate in people with symptoms and signs of gout and to repeat it at least 2 weeks after a flare if the level was below 360 micromol/L during the flare but gout is still strongly suspected. It also recommends aiming for a target serum urate below 360 micromol/L in treat-to-target urate-lowering therapy, and lower than 300 micromol/L in selected cases with tophi or persistent flares.
This page stays lab-focused: uric acid links strongly with gout, but management and medication detail belongs in separate condition-focused content.
Uric acid and the kidneys
Kidney clearance is central to uric acid interpretation. MedlinePlus explains that most uric acid dissolves in blood and is filtered by the kidneys. If the kidneys do not remove enough, uric acid rises. The blood test and the 24-hour urine uric acid test answer slightly different questions, with urine testing being especially relevant when kidney stones are part of the story.
Pre-analytical issues and interferences
MedlinePlus says many medicines can affect uric acid levels, including aspirin and niacin, so clinicians should know what the person is taking. Patients may be asked not to eat or drink for about 4 hours beforehand unless told otherwise. Food and drink patterns also matter: red meat, organ meats, certain seafood, alcohol, and high-fructose corn syrup are among contributors to raised uric acid.
Blood uric acid versus urine uric acid
A blood uric acid test measures what is circulating in blood. A urine uric acid test, often a 24-hour collection, may be used to help investigate kidney stones or uric acid handling more directly. MedlinePlus says the urine version may help determine whether high uric acid is contributing to kidney stones or monitor stone risk in people with gout.
Practical takeaway
A uric acid blood test is mainly about urate handling and context. High uric acid can be linked with gout, kidney disease, kidney stones, chemotherapy-related cell breakdown, medicines, alcohol, and diet factors, but many people with high uric acid do not have active disease. Serum urate is useful, but it makes more sense when read with symptoms, kidney markers, history, and sometimes urine or joint-fluid testing.
Frequently asked questions
What does a uric acid blood test measure?
It measures the amount of uric acid, or serum urate, circulating in the blood.
Does high uric acid always mean gout?
No. High uric acid can occur without gout and may also relate to kidney disease, medicines, alcohol, diet, cancer-treatment effects, or other causes.
Can uric acid be normal during a gout flare?
Yes. NICE says that if serum urate is below 360 micromol/L during a flare and gout is still strongly suspected, the level should be repeated at least 2 weeks after the flare settles.
Do medicines affect uric acid blood tests?
Yes. MedlinePlus says medicines including aspirin and niacin can affect uric acid levels.
What is the difference between blood uric acid and urine uric acid?
Blood uric acid shows what is circulating in blood. Urine uric acid testing, often over 24 hours, can be used when kidney stones or uric acid excretion patterns are being assessed.
Educational only. This page does not provide diagnosis, treatment, or personal medical advice.
Sources: MedlinePlus — Uric Acid Test | MedlinePlus Medical Encyclopedia — Uric acid – blood | NICE — Gout: diagnosis and management (NG219)
How uric acid relates to other tests
- Kidney function — uric acid is filtered by kidneys; eGFR and creatinine are checked when kidney stones or CKD is suspected. See: eGFR Explained
- CRP and ESR — inflammation markers used alongside uric acid during gout flares. See: CRP Explained
- Full blood count — checked when blood cancers or chemotherapy effects are a concern. See: Full Blood Count Explained
- Calcium — kidney stones can involve both uric acid and calcium. See: Calcium Blood Test Explained