Common Blood Tests Explained: CBC, Cholesterol, Thyroid, and What Your Results Mean

Blood tests are used to:

• Screen for conditions such as diabetes, high cholesterol, and anemia before symptoms appear
• Diagnose the cause of symptoms such as fatigue, weight change, or frequent infections
• Monitor chronic conditions and see whether treatment is working
• Check how organs such as the kidneys, liver, and thyroid are functioning
• Review overall health during a yearly checkup

Lab work is often ordered as part of an annual physical checkup. City Prime Care offers diagnostic testing to support this.

Always follow the specific instructions your doctor or lab gives you, since fasting rules can differ depending on which tests are combined. The U.S. National Library of Medicine also keeps a helpful MedlinePlus lab tests guide with details on hundreds of tests.

Reference ranges differ slightly between laboratories, and your doctor interprets results in the context of your age, sex, medicines, and overall health. The table below lists commonly used adult ranges for general understanding only.

Blood sugar results are explained further in our guide to type 2 diabetes early signs and daily management.

A lipid panel measures several types of fat in your blood. LDL is often called bad cholesterol because high levels can build up in artery walls. HDL is known as good cholesterol because it helps remove excess cholesterol. Triglycerides are another type of blood fat that, when high, add to heart risk. The American Heart Association offers more detail on cholesterol and heart health.

The graph below shows how LDL cholesterol levels are commonly grouped. A longer bar means a higher level of concern.

High cholesterol and high blood pressure often travel together, so you may also want to read our guide to high blood pressure numbers and daily management.

Good preparation helps you get accurate results and a smoother visit:

1. Ask your doctor whether you need to fast, and for how long. Water is usually allowed and helps.
2. Take your regular medicines unless your doctor says otherwise, and share a list of everything you take, including supplements.
3. Drink plenty of water beforehand, since being well hydrated makes veins easier to find.
4. Avoid alcohol and heavy, greasy meals the day before a fasting test.
5. Wear a shirt with sleeves that roll up easily.
6. After the draw, press on the site, keep the bandage on for a few hours, and tell staff if you feel dizzy.

An abnormal result does not always mean something is wrong. Consider the following:

• A single value slightly outside the range may be harmless or temporary, caused by dehydration, recent illness, or exercise.
• Doctors often repeat a test or order follow-up testing before making a diagnosis.
• Patterns over time matter more than one number.
• Do not change or stop medicines based on a lab result without speaking to your provider.
• Ask your doctor to explain what the result means for you and what steps, if any, come next.

If you need ongoing follow-up, our primary care and chronic disease management teams can help you track results over time.

More from City Prime Care: Understanding Your Diagnostic Testing Results and Flu vs Cold vs COVID-19.

Trusted external sources: MedlinePlus Lab Tests, American Heart Association: Cholesterol, and American Diabetes Association.

If you have questions about lab work, need testing, or want help understanding your results, City Prime Care can guide you at our Elmhurst, Queens clinic. Please visit our contact page at https://www.cityprimecare.com/contact to get in touch.

Understanding your blood tests takes some of the mystery out of your health. When you know what each test measures, how to prepare, and how to ask good questions, you can work more confidently with your care team to stay on track.

This article is for general education and does not replace personal medical advice. Reference ranges vary by laboratory, so always review your results with a qualified healthcare professional.