Does stress affect blood test results? Yes, and more than you think

Stress is not just a mental state – it affects the whole body. Stress and blood tests are more connected than we think: stress can change some lab results and produce values that do not reflect your usual condition.

How does stress affect blood tests?

• It raises cortisol – a hormone that affects blood glucose, blood pressure, weight and mood. For this reason, blood sugar may come out higher than usual.
• It changes circulation and blood pressure – blood pressure measured at stressful moments often comes out higher.
• It affects immunity – prolonged stress can be associated with more frequent infections and inflammation, which show up in tests such as CRP or white blood cell count.
• It affects hormones – prolactin and thyroid hormones may change temporarily.

Other factors that affect results

• food before the tests – many tests require 8–12 hours of fasting;
• intense physical activity – can raise muscle and liver enzymes;
• alcohol and insufficient sleep;
• certain medicines and supplements – tell the doctor what you are taking.

Tips before your tests

• Don’t arrive rushed or anxious – take a few minutes for deep breathing.
• Avoid intense physical activity for 24 hours before the tests.
• Avoid alcohol the day before.
• Get enough sleep the night before.
• Come fasting when the test requires it; water is allowed.

Careful interpretation

At Dr. Medical Clinic & Lab, every individual is treated as unique – so blood tests are always interpreted by the doctor, in the context of your physical and emotional condition. When a value is outside the normal range without a clear explanation, the doctor may recommend repeating it. See the tests we perform under Laboratory or Packages 2026.