Our bodies are remarkably good at telling us when something is wrong. Yet many of us dismiss symptoms as minor inconveniences or signs of getting older, when they could actually be warning signs of underlying health conditions that need attention.
The good news is that a simple blood test can often provide clarity, helping to identify or rule out potential causes of your symptoms. Early detection is key to successful treatment of many conditions, so paying attention to what your body is telling you could make a significant difference to your health outcomes.
Here are 10 health symptoms you should never ignore — and how blood testing can help.
1. Persistent Fatigue
Everyone feels tired occasionally, but if you are constantly exhausted despite getting adequate sleep, it is time to investigate further. Persistent fatigue that does not improve with rest can indicate:
Blood tests that help: Full blood count, iron studies, vitamin B12, folate, thyroid function tests, HbA1c, vitamin D.
2. Unexplained Weight Changes
Gaining or losing weight without changes to your diet or exercise habits warrants investigation. Unexplained weight gain may indicate thyroid problems, hormonal imbalances, or metabolic issues. Unexplained weight loss can be a sign of diabetes, hyperthyroidism, or more serious conditions.
Blood tests that help: Thyroid function tests, HbA1c, fasting glucose, cortisol levels.
3. Excessive Thirst and Frequent Urination
If you find yourself constantly thirsty and making frequent trips to the toilet, these are classic warning signs of diabetes. High blood sugar causes the kidneys to work harder to filter excess glucose, leading to increased urination and subsequent dehydration.
Blood tests that help: Fasting glucose, HbA1c, kidney function tests. For more information, read our comprehensive guide to understanding the A1C blood test.
4. Shortness of Breath
Feeling breathless during normal activities or at rest should not be ignored. While it can have many causes, including heart and lung conditions, blood-related causes include severe anaemia (where your blood cannot carry enough oxygen) and certain infections.
Blood tests that help: Full blood count, iron studies, B12 and folate, inflammatory markers (CRP, ESR).
5. Unusual Bruising or Bleeding
If you bruise easily, notice unexplained bruises, or experience prolonged bleeding from minor cuts, this could indicate problems with your blood's ability to clot. Potential causes include low platelet counts, clotting factor deficiencies, or liver problems.
Blood tests that help: Full blood count (including platelet count), coagulation studies, liver function tests. Learn more about what liver function tests reveal about your health.
6. Changes in Skin or Hair
Your skin and hair often reflect your internal health. Symptoms to watch for include:
These changes may indicate thyroid disorders, anaemia, nutritional deficiencies, liver problems, or kidney disease.
Blood tests that help: Thyroid function tests, iron studies, vitamin D, liver function tests, kidney function tests.
7. Persistent Muscle Aches and Weakness
While occasional muscle soreness after exercise is normal, persistent muscle pain or weakness without obvious cause deserves attention. Potential causes include vitamin D deficiency, thyroid dysfunction, electrolyte imbalances, and inflammatory conditions.
Blood tests that help: Vitamin D, calcium, thyroid function tests, CRP, ESR, creatine kinase (muscle enzyme). Our article on the cortisol blood test explains how stress hormones can also affect muscle health.
8. Feeling Cold All the Time
If you are constantly reaching for extra layers while others are comfortable, your thyroid could be to blame. Hypothyroidism slows your metabolism, reducing heat production and making you feel cold. Anaemia can also cause cold intolerance as your blood carries less oxygen to tissues.
Blood tests that help: Thyroid function tests, full blood count, iron studies.
9. Brain Fog and Difficulty Concentrating
Struggling to focus, forgetting things, or feeling mentally sluggish can be frustrating and concerning. While these symptoms have many potential causes, treatable conditions include:
Blood tests that help: Thyroid function tests, vitamin B12, iron studies, HbA1c, CRP.
10. Mood Changes and Depression
While mental health conditions have complex causes, physical health problems can contribute to or mimic depression and anxiety. Thyroid disorders are particularly well-known for affecting mood — hypothyroidism often causes depression, while hyperthyroidism can cause anxiety. Vitamin deficiencies, particularly B12, folate, and vitamin D, are also associated with mood disorders.
Blood tests that help: Thyroid function tests, vitamin B12, folate, vitamin D, full blood count.
Why Blood Tests Matter
Blood tests are powerful diagnostic tools because they can:
Many of the conditions that cause the symptoms listed above are highly treatable when caught early. A simple blood test can be the first step toward feeling better.
When to Get Tested
Consider blood testing if you:
Do not wait for symptoms to become severe. Proactive testing can identify problems early when they are easier to treat.
Comprehensive Blood Testing in London
At Private Blood Tests London, we offer a wide range of blood tests at our CQC-registered clinic in South Kensington. Whether you need a single specific test or a comprehensive health screen, our experienced healthcare team is here to help.
We understand that experiencing unexplained symptoms can be worrying. Our professional, efficient service provides quick results delivered securely, giving you the clarity you need to take the next steps for your health.
Explore our [health screening packages](/health-screening), [all available tests](/all-blood-tests), and [test prices](/blood-test-prices).
For an overview of essential tests to consider, read our guide to the [top 10 important blood tests](/blog/top-10-important-blood-tests).
Do not ignore what your body is telling you — book your blood test today and take control of your health.