---
title: "What blood tests are used for muscle weakness?"
type: symptom
url: "https://www.test-well.com/symptoms/muscle-weakness"
symptom: Muscle weakness
aliases:
  - weak muscles
  - muscle fatigue blood test
  - muscle aches and weakness
reviewed_at: 2026-09-06
review_status: reviewed
date_published: 2026-09-05
lab_fee_usd: 6
---

# What blood tests are used for muscle weakness?

> Muscle weakness with no obvious cause is checked with creatine kinase (muscle breakdown), a comprehensive metabolic panel (electrolytes, kidney and liver), magnesium, vitamin D, TSH and morning cortisol. Statins and other medications are a frequent culprit, so the medication list matters as much as the labs.


## When should you see a clinician instead of ordering a test?

- Sudden weakness on one side, facial droop or trouble speaking — call emergency services
- Weakness that is spreading, trouble swallowing or breathing, or dark (cola-colored) urine — seek care the same day

## Why these tests for muscle weakness?

Creatine kinase rises when muscle fibers are damaged — by statins, intense exercise, injury or inflammatory muscle disease. Low potassium, sodium, calcium or magnesium cause weakness and cramps, and the CMP catches most of them. Vitamin D deficiency produces proximal weakness (rising from a chair), thyroid disease in either direction causes weakness, and adrenal insufficiency — rare — is screened with morning cortisol.

## Which conditions do these tests help evaluate?

- [Chronic Fatigue](https://www.test-well.com/conditions/chronic-fatigue) — Thyroid, iron, B12, vitamin D and inflammation markers for persistent tiredness.
- [Thyroid Problems](https://www.test-well.com/conditions/thyroid-problems) — TSH, Free T4/T3 and antibodies to evaluate an under- or over-active thyroid.

## Which tests, and what do they cost?

| Test or panel | Type | Price | All-in (one item + $6 fee) | Fasting | Results |
| --- | --- | --- | --- | --- | --- |
| [Fitness & Performance Panel](https://www.test-well.com/tests/fitness-performance-panel) | Panel (8 tests) | $119.99 | $125.99 | Yes | 2–5 business days |
| [General Wellness Panel](https://www.test-well.com/tests/general-wellness-panel) | Panel (4 tests) | $89.99 | $95.99 | Yes | 1–3 business days |
| [Creatine Kinase (CK)](https://www.test-well.com/tests/creatine-kinase-test) | Test | $18.99 | $24.99 | No | 1–3 business days |
| [Comprehensive Metabolic Panel](https://www.test-well.com/tests/comprehensive-metabolic-panel) | Test | $22.99 | $28.99 | Yes | 1–3 business days |
| [Magnesium](https://www.test-well.com/tests/magnesium) | Test | $19.99 | $25.99 | No | 2–4 business days |
| [Vitamin D, 25-Hydroxy](https://www.test-well.com/tests/vitamin-d) | Test | $41.99 | $47.99 | No | 1–3 business days |
| [TSH (Thyroid Stimulating Hormone)](https://www.test-well.com/tests/tsh) | Test | $26.99 | $32.99 | No | 1–3 business days |
| [Cortisol (AM)](https://www.test-well.com/tests/cortisol-am) | Test | $26.99 | $32.99 | No | 2–4 business days |

Prices are cash-pay; every order adds one $6.00 lab processing fee. Physician authorization included.

## Common questions

### Should I stop exercising before a CK test?

Avoid strenuous exercise for 48 hours before the draw; hard workouts raise CK for days and can mimic a muscle problem.

## Related

- [What blood tests should you get for fatigue?](https://www.test-well.com/symptoms/fatigue)
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- [All symptoms](https://www.test-well.com/symptoms)
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---

Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-06. Review policy: https://www.test-well.com/editorial-policy

Canonical page: https://www.test-well.com/symptoms/muscle-weakness
Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt

Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.