Nursing care
Deep tendon reflex grading: what 0 to 4+ means and the grades that change magnesium care
Written and reviewed by Kevin Patel, MSN, RN, CCRN · 4 min read · Updated November 2026
Short answer
On the deep tendon reflex grading scale, 2+ is normal, 1+ is diminished, 0 is absent, 3+ is brisker than normal without clonus, and 4+ is hyperactive with clonus. On the NCLEX the scale matters most in two places: brisk reflexes as a warning sign in preeclampsia, and fading or absent patellar reflexes as a sign of magnesium toxicity.
The five reflex grades and what the nurse does at each
Reflexes are graded on a 0 to 4+ scale with 2+ as the expected finding. Open RN Nursing Skills gives the grades as absent, hypoactive, normal, hyperactive without clonus, and hyperactive with clonus, where clonus means repeated involuntary muscle contractions after the tap.
| Grade | Meaning | Usual nursing response |
|---|---|---|
| 0 | No reflex response | Retest with the limb relaxed; on magnesium sulfate, treat as a toxicity sign and act now |
| 1+ | Present but weaker than expected | Compare sides and with the last grade; on magnesium, a falling trend is reported |
| 2+ | Expected response | Document and continue the routine schedule |
| 3+ | Brisker than expected, no clonus | In pregnancy with high blood pressure, check headache, vision and blood pressure and report |
| 4+ | Very brisk with clonus | Report promptly; sustained clonus points to an upper motor neuron problem |
A single number means less than the pattern around it. MSD Manuals stresses noting any asymmetric increase or decrease, and associates depressed reflexes with lower motor neuron problems and increased reflexes with upper motor neuron problems.
Getting a fair reflex before you call it absent
Open RN notes that reflex testing is not part of a routine adult nursing neuro check but is done in specialty settings, and obstetric units checking patellar reflexes during magnesium therapy are the classic example. Seat the client with the leg hanging freely, tap the patellar tendon briskly, and watch for extension of the lower leg.
Tensing the muscle can block the reflex. Open RN advises repeating the test after encouraging the client to relax before grading a reflex as absent or weak. MSD Manuals describes reinforcement for the legs: the client locks the hands together and pulls them apart as the tendon is tapped. A reflex that appears only with reinforcement is graded as present, not 0.
Why the patellar reflex guides magnesium sulfate monitoring
The magnesium sulfate label on DailyMed lays out the thresholds. Normal serum magnesium is 1.3 to 2.1 mEq/L, and levels of about 2.5 to 5 mEq/L are usually enough to control seizures. Reflexes start to weaken once levels pass 4 mEq/L and may disappear near 10 mEq/L, where respiratory paralysis becomes a risk. The label names a present knee jerk and a respiratory rate of about 16 or more per minute as clinical signs that the regimen is safe, and says urine output should be kept at 100 mL every 4 hours.
Brisk reflexes point the other way. MSD Manuals lists hyperreflexia among the severe features of preeclampsia and says hospitalized clients are checked often for blood pressure and reflexes. So a client admitted at 3+ who settles to 2+ on magnesium is responding as expected, while a slide down to 1+ or 0 is the warning. The bedside priorities for an absent reflex are covered on the linked priorities page.
Hypothetical practice case: a reflex trend during an infusion
Hypothetical scenario for practice, not a real exam item, with made-up figures: a client with preeclampsia with severe features starts magnesium sulfate. Patellar reflexes are 3+ with no clonus at the start, 2+ at the four-hour check, 1+ at hour six, and absent at hour eight with a respiratory rate of 11 per minute.
Worked example
- 3+ to 2+: hyperreflexia settling, an expected response to therapy.
- 2+ to 1+: reflexes are weakening; recheck both sides, count respirations, check urine output and report the trend.
- 1+ to 0 with respirations below about 16: two label signs of magnesium excess at once.
- Act: stop the infusion per protocol, stay with the client, notify the provider, and have the calcium antidote ready as ordered.
The trap answer charts the absent reflex as resolution of hyperreflexia. Reflexes falling from normal to absent is not improvement. MSD Manuals lists a sudden decrease in reflex reactivity among the findings for which calcium gluconate may be given after magnesium therapy.
Sources and further reading
Open RN Nursing Skills 2e: 6.9 Assessing Reflexes. 0 to 4+ grading with 2+ normal and 4+ meaning clonus, reflex testing used in specialty units rather than routine nursing checks, seated position, repeating after relaxation before calling a reflex absent, patellar reflex technique.
MSD Manual Professional Version: How To Assess Reflexes. Noting asymmetric increase or depression, reinforcement maneuver, sustained clonus indicating an upper motor neuron disorder, lower motor neuron lesions depressing reflexes.
DailyMed: Magnesium Sulfate in Water Injection, Solution (Hospira) label. Normal serum magnesium range, therapeutic range, reflexes diminishing above 4 mEq/L and absent near 10 mEq/L with respiratory paralysis risk, patellar reflex and respirations of about 16 or more as safety signs, urine output of 100 mL every 4 hours.
MSD Manual Professional Version: Preeclampsia and Eclampsia. Hyperreflexia as a severe feature, frequent checks of blood pressure and reflexes in hospitalized clients, calcium gluconate for very high magnesium levels or a sudden decrease in reflex reactivity.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our neurological practice questions are the closest set to what this page covers.
Common questions
What is a normal DTR grade?
2+ is the normal grade on the 0 to 4+ scale. Grades of 1+ and 3+ can still occur without disease, so the trend over time and any difference between sides matter more than one reading.
What DTR grade indicates magnesium toxicity?
A falling grade, reaching 0 (absent patellar reflex), is the classic sign. The magnesium sulfate label states reflexes weaken above about 4 mEq/L and may disappear near 10 mEq/L, where breathing can stop. An absent reflex needs immediate action under protocol.
What does a deep tendon reflex grade of 3+ mean?
A brisker than normal reflex without clonus. Alone it may not mean much, but in a pregnant client with high blood pressure it is a warning sign of preeclampsia with severe features, so check headache, vision and blood pressure and report.