CBC, A1C, Lipid Panel: What Common Blood Tests Show, and Whether You Need to Fast
A plain-language guide to the blood tests you're most likely to be ordered, what they measure, how long to fast before them, and what can be tested during an urgent care visit.
The blood tests ordered most often are a complete blood count (CBC), a metabolic panel, a lipid (cholesterol) panel and an A1C. Together they check your blood cells, kidneys, liver, blood sugar and cholesterol. Most don't require fasting. A lipid panel or fasting glucose test may ask you to skip food for 8 to 12 hours, so check your instructions. Some quick tests, like urinalysis, pregnancy tests and blood sugar checks, can be run during an urgent care visit.
Complete blood count (CBC)
A CBC counts the cells in your blood:
- Red blood cells and hemoglobin, which carry oxygen. Low levels can mean anemia.
- White blood cells, which fight infection. A high count can point to an infection or inflammation.
- Platelets, which help blood clot.
A CBC with differential also breaks white cells down by type, which helps tell a bacterial infection from a viral one.
Basic or comprehensive metabolic panel (BMP or CMP)
These measure blood sugar, electrolytes such as sodium and potassium, and kidney function. A comprehensive panel adds liver tests and protein levels. They're often used to check for dehydration, kidney problems or the effects of a medicine.
A1C
A1C shows your average blood sugar over the past two to three months. It's used to screen for and track diabetes and prediabetes. It doesn't require fasting.
Lipid panel
A lipid panel measures total cholesterol, LDL ("bad") cholesterol, HDL ("good") cholesterol and triglycerides. It helps estimate your risk of heart disease. Many labs no longer require fasting for it, but some still do.
How long to fast before blood work
- Usually no fasting: CBC, A1C, thyroid tests and most others
- Often 8 to 12 hours: fasting glucose, and a lipid panel if your provider asks for a fasting one
- While fasting: drink water, which also makes the draw easier. Skip coffee, juice and gum. Take your usual medicines unless you've been told not to.
When in doubt, ask whoever ordered the test.
What can be tested at urgent care
During a visit, AfterOurs can run point-of-care tests such as urinalysis, pregnancy tests and blood sugar checks, with most results ready before you leave. Some blood tests are sent to a reference lab, and results are shared when they come back. See our in-clinic lab tests page. If you're due for a routine check, our post on getting an annual physical without a primary care doctor explains your options.
At an AfterOurs clinic, a standard self-pay visit is $175, and a self-pay in-clinic visit never costs more than $330. We contract with all major commercial and government plans, including Colorado Medicaid and Medicare. See the cost and insurance page.
Go to the ER or call 911 if you've been told a result is dangerously abnormal and to seek care right away, or if you have chest pain, severe weakness, confusion, fainting, or very high or very low blood sugar with vomiting, confusion or trouble staying awake.
Where to find us
Four clinics across metro Denver, all ages welcome, se habla español:
- Hampden (Southeast Denver): 8 AM–11 PM daily
- Littleton: 8 AM–11 PM daily
- Thornton: 8 AM–11 PM daily
- Highlands: Mon–Fri 5–11 PM, Sat–Sun 8 AM–11 PM
Walk in, or book online.
Medically reviewed by Peter Martinuzzi, MD
This article is general health information, not medical advice for your situation. If you are worried, come in or book a telehealth visit — and if it is an emergency, call 911.