Proinsulin test (beta-cell stress marker) Biomarker Testing
A proinsulin test measures a precursor to insulin that can rise with beta-cell stress and insulin resistance, with convenient Quest lab ordering via Vitals Vault.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
Proinsulin is the “starter” molecule your pancreas makes before it becomes insulin. Most of it gets processed inside beta cells, and only a small amount normally shows up in your blood.
When your beta cells are under strain—often from insulin resistance—more proinsulin can leak into circulation. That is why proinsulin is sometimes used as a beta-cell stress marker, especially when you are trying to understand early metabolic risk or unusual insulin patterns.
A proinsulin result is not a diagnosis by itself. It becomes most useful when you interpret it alongside fasting glucose, insulin (or C‑peptide), and your overall clinical picture.
Do I need a Proinsulin test?
You may consider a proinsulin test if you are investigating insulin resistance, prediabetes risk, or why your insulin-related labs do not match how you feel. For example, you might have normal fasting glucose but symptoms that suggest blood-sugar swings, or you might have a family history of type 2 diabetes and want a deeper look at pancreatic stress.
This test can also be helpful when your fasting insulin is high (or unexpectedly low) and you want more context about how hard your beta cells are working. In some cases, clinicians use proinsulin as part of a broader evaluation of unexplained hypoglycemia (low blood sugar), especially when paired with glucose, insulin, and C‑peptide collected at the same time.
You usually do not need proinsulin as a first-line screening test. Many people start with fasting glucose, HbA1c, and a lipid panel, and then add proinsulin when the goal is to clarify insulin secretion patterns or beta-cell strain.
Testing supports clinician-directed care and shared decision-making, but it is not meant for self-diagnosis or to replace medical evaluation when you have concerning symptoms.
Proinsulin is measured with a laboratory immunoassay (typically performed in a CLIA-certified lab); results should be interpreted with your clinician and other metabolic markers rather than used as a standalone diagnosis.
Lab testing
Order labs to measure Proinsulin
from $349.42 at Quest Diagnostics
About 1 week
Schedule online — results typically within a week
Clear next steps
Guidance included, with follow-up care available
HSA / FSA
Eligible for pre-tax health spending accounts
Get this test with Vitals Vault
Vitals Vault lets you order proinsulin testing without a referral and complete your blood draw at a participating Quest location. This is useful when you want to move from “I’m not sure what these symptoms mean” to a concrete data point about beta-cell stress.
If you already have glucose and insulin results, adding proinsulin can make the pattern clearer—especially when you are trying to understand whether your pancreas is compensating effectively or showing signs of strain. If you are starting from scratch, you can order proinsulin alongside other metabolic labs so your result is easier to interpret.
After your results post, you can use PocketMD to ask targeted questions (for example, what your proinsulin suggests in the context of your fasting glucose and insulin) and to plan what to recheck and when.
Key benefits of Proinsulin testing
- Adds a beta-cell stress signal that can rise before glucose or HbA1c clearly worsen.
- Helps distinguish “high insulin because of resistance” from patterns that suggest impaired insulin processing.
- Provides context when fasting insulin is high, borderline, or doesn’t match your symptoms.
- Supports earlier risk stratification for progression from insulin resistance to prediabetes.
- Can be paired with glucose, insulin, and C‑peptide to evaluate unusual hypoglycemia patterns under clinician guidance.
- Improves interpretation of metabolic panels by clarifying insulin secretion and processing rather than glucose alone.
- Makes it easier to track change over time when you repeat testing and review trends in PocketMD.
What is Proinsulin?
Proinsulin is the precursor molecule your pancreatic beta cells produce to make insulin. Inside the beta cell, proinsulin is normally “cut” into insulin and C‑peptide, and then insulin is released to help move glucose from your bloodstream into cells.
Because most proinsulin is processed before release, blood levels are usually low compared with insulin. When beta cells are stressed or their processing machinery is less efficient, more intact proinsulin can be released into the bloodstream. That is why proinsulin is often discussed as a marker of beta-cell strain and early metabolic dysfunction.
Proinsulin is not the same as insulin. Insulin reflects how much hormone is being secreted (and how much remains in circulation), while proinsulin can reflect how well the beta cell is converting precursor into mature insulin under demand.
How it relates to insulin resistance
With insulin resistance, your tissues respond less effectively to insulin, so your pancreas often compensates by producing more. Over time, the increased workload can lead to higher proinsulin release, which may signal that beta cells are working harder to keep glucose in range.
Why clinicians sometimes look at ratios
Some clinicians consider the proinsulin-to-insulin ratio (or proinsulin relative to C‑peptide) to understand insulin processing efficiency. The exact cutoffs and usefulness vary by lab method, so it is best used for pattern recognition and trend tracking rather than a single “pass/fail” number.
What do my Proinsulin results mean?
Low proinsulin levels
A low proinsulin result is often normal, especially if your glucose and insulin are also in a healthy range. It can suggest that your beta cells are not under heavy demand and are efficiently processing proinsulin into insulin. If you are being evaluated for hypoglycemia, a low proinsulin level during a low-glucose episode may make excess insulin secretion less likely, but interpretation depends on the full “critical sample” (glucose, insulin, C‑peptide, and more).
Optimal (in-range) proinsulin levels
An in-range proinsulin result generally suggests typical insulin precursor processing for that lab’s reference interval. The most important next step is checking whether it matches your other markers: fasting glucose, HbA1c, fasting insulin (or C‑peptide), triglycerides, and waist/weight trends. If your proinsulin is in range but insulin is high, the pattern may still fit insulin resistance, just without a strong proinsulin “stress” signal at that moment.
High proinsulin levels
A high proinsulin result can indicate beta-cell strain or less efficient conversion of proinsulin into insulin, which is commonly seen in insulin resistance and can appear as metabolic risk progresses. It does not automatically mean you have diabetes, and it is not a cancer screen. If your result is high, it is most informative to review it alongside fasting glucose, HbA1c, insulin (or C‑peptide), and sometimes an oral glucose tolerance test when clinically appropriate.
Factors that influence proinsulin
Fasting status matters because eating stimulates insulin secretion and can raise proinsulin; most comparisons are made using a fasting sample. Kidney function can affect clearance of insulin-related peptides, which may shift results. Medications that change insulin secretion or sensitivity (such as insulin, sulfonylureas, GLP‑1 receptor agonists, and steroids) can alter interpretation, so your medication list should be part of the conversation. Acute illness, significant stress, and recent intense exercise can also temporarily change glucose-insulin dynamics.
What’s included
- Proinsulin
Similar tests to consider
Frequently Asked Questions
Do I need to fast for a proinsulin test?
Most proinsulin tests are interpreted best when you are fasting, because food intake triggers insulin secretion and can raise proinsulin. Follow the collection instructions on your order, and tell your clinician whether you were fasting when the sample was drawn.
What is the difference between proinsulin, insulin, and C‑peptide?
Proinsulin is the precursor molecule made in beta cells. It is normally processed into insulin and C‑peptide, which are released together. Insulin reflects the active hormone in circulation, while C‑peptide helps estimate how much insulin your body is producing (especially if you use injected insulin).
Does high proinsulin mean I have diabetes?
Not by itself. High proinsulin can be a sign of beta-cell strain and is often seen with insulin resistance, but diabetes is diagnosed using glucose-based criteria (such as fasting glucose, HbA1c, or an oral glucose tolerance test). Your overall pattern matters more than a single marker.
Can medications affect my proinsulin result?
Yes. Medications that increase insulin secretion or change insulin sensitivity can shift proinsulin and related markers. Examples include insulin, sulfonylureas, GLP‑1 receptor agonists, and corticosteroids. Do not stop medications for testing unless your clinician specifically instructs you to.
Is proinsulin used to evaluate insulinoma or other causes of hypoglycemia?
It can be part of a clinician-directed workup for unexplained hypoglycemia, but it is not used alone. Typically, proinsulin is interpreted with a simultaneous low glucose value plus insulin and C‑peptide (and sometimes additional tests) collected during symptoms or a supervised evaluation.
What is a proinsulin-to-insulin ratio and should I calculate it?
The proinsulin-to-insulin ratio is a way some clinicians assess insulin processing efficiency and beta-cell stress. Because assays and reference ranges vary, the ratio is most useful when your clinician applies lab-specific context and compares it with your other metabolic markers and trends over time.
How often should I recheck proinsulin?
There is no single schedule for everyone. If you are using it to track metabolic risk or response to lifestyle or medication changes, many people recheck in a similar window to other metabolic labs (often a few months), but your timing should match your goals and clinician guidance.