How to Prepare for a Prolactin Blood Test: High Levels

Preparing for a prolactin blood test involves following your laboratory’s specific instructions to ensure your results are accurate. Because prolactin levels are highly sensitive to daily activities and stress, a few simple steps can help prevent temporary spikes.

Key preparation steps to keep in mind:

• Follow Lab Instructions: Only fast if your doctor or lab specifically tells you to.
• Keep Taking Medications: Never stop prescribed medicines unless explicitly instructed by your doctor.
• Plan for Rest: Arrive early so you can sit quietly for 15 to 30 minutes before the blood draw.

Why Preparation Matters

Prolactin is a hormone that naturally fluctuates over the course of the day ^[1]. The body quickly releases it in response to physical changes, emotional stress, food, and sleep ^[2]. By controlling these daily variables, you and your doctor can ensure that a high test result is truly persistent hyperprolactinemia (an ongoing elevation of prolactin) rather than a temporary rise ^[3].

It is also important to tell your doctor if you are pregnant or breastfeeding, as these naturally raise prolactin to expected, healthy levels ^[4].

Timing and Fasting

• Coordinate Your Draw Time: Prolactin levels naturally rise at night while you sleep and vary significantly throughout the daytime ^[5]. Many doctors recommend testing in the morning, but rather than going immediately upon waking, they may want you to wait a specific amount of time (such as 2 to 3 hours) after you wake up ^[1]. Always follow your clinic’s specific timing instructions.
• Fast Only if Instructed: While food intake can affect your prolactin levels ^[6], fasting is not universally required for this test ^[7]. Only fast if your doctor or lab specifically asks you to. If you have conditions like diabetes, ask your doctor for personalized advice about how to safely prepare.

Activities to Discuss With Your Doctor

Certain physical activities can cause a temporary surge in hormone levels. To avoid this, doctors frequently recommend avoiding the following activities for 24 hours prior to your blood draw:

• Vigorous Exercise: Intense physical activity can temporarily elevate prolactin levels ^[2].
• Sexual Activity: Ejaculation and sexual intimacy are known to cause rapid, temporary spikes in prolactin ^[8].
• Breast and Nipple Stimulation: Physical stimulation of the chest or nipples triggers a rapid release of prolactin ^[4].

If you do engage in any of these activities before your test, do not panic or assume your result is invalid. Simply mention it to your healthcare team so they can interpret your results accurately.

Managing Stress on the Day of the Test

Stress—including the anxiety of getting a blood test itself—can cause a significant temporary increase in prolactin ^[3]. One study showed that when patients with a mildly elevated initial test rested quietly before a second test, their prolactin levels returned to normal in 54% of cases ^[3].

If your initial test is slightly high, your doctor will likely review your symptoms, medications, and other health factors before simply repeating the test under calm, controlled conditions ^[9].

• Arrive Early and Rest: Plan to sit quietly in the waiting room for 15 to 30 minutes before the needle stick ^[10]. This rest period allows your body to calm down, preventing a stress-induced spike in your results.
• Ask About a Temporary IV Line: If you have severe needle anxiety, your doctor might recommend using an indwelling cannula (a small, temporary IV line placed in a vein) ^[9]. A nurse places the IV line, lets you rest for about 30 minutes, and then draws the blood through the line without a second needle stick ^[3][10]. Note that this must be arranged in advance and is not available at every laboratory.