Blood electrolytes (potassium, sodium, calcium)
electrolyte panel · potassium test · sodium test · calcium test · basic metabolic panel
This is a blood test from a vein. It shows the level of salts in your blood that your heart, muscles, and nerves need.
For weakness, cramps, skipped heartbeats, while taking water pills, after vomiting or diarrhea, or with kidney disease.
⏱ Duration: the blood draw takes a few minutes; results usually come the next day
Be sure to tell your doctor
How to prepare
- Food. Usually fasting: no food for 8 to 12 hours. Plain water is fine. Check with the lab.
- The day before. For 24 hours, no alcohol and no hard workouts. Best not to smoke in the morning.
- Medicines. Do not stop them on your own. Tell your doctor what you take. They will decide if anything should change.
What to bring
- Your test request form
- Your ID
How it goes
- You sit down and rest your arm on the armrest
- A band is tightened above your elbow for a short time
- Do not pump your fist hard. It can make potassium look higher
- The skin is wiped with antiseptic
- A quick prick, and blood fills a tube
- The needle comes out, and a cotton pad is pressed on the spot
What you'll feel
- A quick prick, like a pinch
- Sometimes slight dizziness. Tell the nurse
Afterwards
- Press the cotton pad for 3 to 5 minutes and keep your arm straight
- You can eat right away and go back to your usual day
- Results usually come in 1 day. The lab will tell you when
Common questions
Why can potassium come out too high?
If the band was on too long or you squeezed your fist hard. Then the doctor will ask you to repeat the test.
Do I need to fast?
Usually yes. The test is done in the morning before eating. Check with the lab.