The Lake Louise Score — How AMS Is Officially Diagnosed
The Lake Louise Score is the standardized system doctors and researchers use to diagnose acute mountain sickness. It requires a headache plus symptoms in three other categories — GI, fatigue/weakness, and dizziness — each scored 0–3. A total score of 3+ with a recent altitude gain = AMS. Knowing this system helps you honestly assess yourself rather than rationalizing away early symptoms.
The Scoring System
| Symptom Category | 0 = None | 1 = Mild | 2 = Moderate | 3 = Severe |
|---|---|---|---|---|
| Headache (required for AMS diagnosis) | None | Mild, doesn't interfere | Moderate, annoying | Severe, incapacitating |
| GI symptoms (nausea, vomiting, appetite loss) | None | Poor appetite OR nausea | Moderate nausea/vomiting | Severe, can't eat/drink |
| Fatigue / weakness | Normal | Mild tiredness | Moderate fatigue | Severe exhaustion |
| Dizziness / lightheadedness | None | Mild | Moderate | Severe |
Reading Your Score
- Score 0–2: not AMS — mild discomfort is normal at altitude; keep ascending cautiously
- Score 3–5 with headache: mild AMS — STOP ascending; rest, hydrate, treat symptoms; do NOT sleep higher until symptoms resolve
- Score 6+ with headache: moderate-to-severe AMS — descend; this isn't "wait and see" territory
- The headache rule: without a headache, a high score is probably something else (dehydration, exhaustion, GI bug) — but at altitude, headache is the hallmark of AMS
How to Use It on the Trail
- Score yourself every evening — at the teahouse, honestly assess each category; the pattern matters more than a single day
- Score your trek partners too — people minimize their own symptoms; an outside observer catches what you rationalize
- Track the trend — a score of 4 that's improving is different from a 4 that's getting worse
- Don't argue with a rising score — the score is a decision tool, not a debate; when it says descend, descend
Limitations — What the Score Misses
- It's for AMS only — HAPE (lung fluid) and HACE (brain swelling) have separate, more serious criteria; the Lake Louise score doesn't capture them
- Self-reporting bias — people underestimate their own symptoms, especially when they don't want to descend
- The "feels like a hangover" test — as a practical shortcut: AMS feels like a bad hangover; if you feel like you drank 10 beers and did no exercise, it's probably AMS
The Trend Is the Signal — Daily Scoring
- Score every evening — the daily pattern matters more than a single day; a stable 3 is different from a worsening 3
- Improving vs worsening — a 4 trending down after rest is different from a 4 trending up; the direction is the information
- Score your partners — self-reporting minimizes; the outside observer catches what the patient rationalizes away
- Record it — the written score prevents the "I feel fine" revisionism; yesterday's number does not get reinterpreted by today's optimism
- The tool not the debate — when the score says descend, the discussion is over; the score exists to remove the argument
Beyond the Score — When Symptoms Outrun the Categories
- The ataxia override — inability to walk heel-to-toe is HACE territory regardless of the Lake Louise score; the clinical signs trump the score
- The breathlessness override — breathless at rest, gurgling, pink froth is HAPE regardless of score; the pulmonary signs are the emergency
- The severe end — the score's ceiling is AMS; symptoms beyond it (confusion, ataxia, pulmonary edema) are the severe diagnoses the score does not capture
- The shortcut that works — AMS feels like a bad hangover; if you feel like you drank 10 beers without the exercise to justify it, that is AMS until proven otherwise
Common Questions
The Scoring System
The Lake Louise Score quantifies AMS severity — headache (the required symptom) plus gastrointestinal symptoms, fatigue/weakness, dizziness, and sleep difficulty, each scored 0–3. Score of 3+ (mild) or 5+ (moderate-severe) with the altitude context indicates AMS. The score is the diagnostic tool, not just the symptom list — it standardizes what "feeling bad at altitude" means clinically.
Self-Assessment Limits
The score is a tool, not a diagnosis — self-scoring at altitude misses the severity that others observe (the confused patient does not accurately self-assess). Use the score for monitoring; trust the companion's observation for the severity. The score that says mild AMS does not exclude the progression that the trained eye catches.
The Scoring System
The Lake Louise Score asks five questions: headache, gastrointestinal symptoms (nausea/appetite loss), fatigue/weakness, dizziness/lightheadedness, and sleep difficulty. Each scores 0 (none) to 3 (severe); a score of 3+ including headache indicates AMS. The scoring standardizes the assessment — removes the "it might be nothing" uncertainty.
The Limitations
The score is a screening tool, not a diagnosis — it does not detect HACE (cerebral edema) or HAPE (pulmonary edema) which require different assessment. The score's false reassurance (a low score does not mean no altitude problem if the symptoms are severe) is the limitation. Use it to flag AMS, not to rule out serious altitude illness.
The Self-Assessment Limit
The Lake Louise score is the screening tool — not the diagnosis. The self-reported symptoms (the headache, the dizziness, the fatigue, the nausea) produce the score that indicates possible AMS. The score does not distinguish the AMS from the migraine, the hangover, the exhaustion, or the illness that produces similar symptoms. The clinician's assessment provides the context the score alone does not.
The Practical Use
On the trail, the score's function is the awareness — the symptom checklist that prompts the descent consideration rather than the definitive measure. The rising score over the days is the meaningful trend; the single score is less informative. For the trekker, the score that is increasing is the signal that the descent should be considered.
The Scoring Components
Lake Louise score: the headache (the mandatory symptom), plus the GI symptoms, the fatigue/weakness, the dizziness, and the AMS clinical score. The score ≥3 with the headache after the ascent = AMS diagnosis. For the trek assessment, the score that standardizes the evaluation.
The Limitation
The score has limitations — it may miss the early AMS or overdiagnose the mild symptoms; the clinical judgment beyond the score. For the borderline score with the concerning trend, the clinical assessment prevails.
The Scoring
Lake Louise scoring: the headache + dizziness + fatigue + GI symptoms + sleep difficulty that are each rated 0-3. The total score that classifies the AMS severity. For the self-assessment, the scoring that quantifies the symptoms.
The Threshold
AMS threshold: Lake Louise score 3-5 = mild AMS, 6+ = moderate/severe. For the trekker with the score 3+, the no-ascent until the resolution; the score 6+ warrants the descent consideration.
The Score Components
Lake Louise components: the headache, the dizziness, the fatigue, the GI symptoms (the nausea/vomiting), and the sleep difficulty that are each scored 0-3. For the self-assessment, the score that is totaled.
The Application
For the trek, the Lake Louise that is used for the self-assessment — the score that determines the ascent or the descent decision.
The Score
Lake Louise score — the AMS that is scored (the headache, the nausea, the dizziness, the fatigue, the sleep, the overall). For the assessment, the score that guides.
The Threshold
Lake Louise threshold — the score that indicates the AMS (the mild vs the moderate vs the severe). For the interpretation, the score that is contextualized.
The Score Value
Lake Louise Score — the free (the self-assessment that requires no equipment). For the AMS screening, the score that is the free tool.
The Consultation
Lake Louise + consultation — the assessment (~$10-25 if the uncertain). For the borderline, the professional that is consulted.
The Free Tool
Lake-Louise score — the free (the self-assessed that is the diagnostic). For the symptom, the scored that is the standard.
The Confirmation
Lake-Louise clinical — the ~$40 (the assessed that confirms). For the ambiguous, the evaluated that is the second opinion.
What is the Lake Louise Score?
The standardized system doctors use to diagnose acute mountain sickness — headache (required) plus symptoms in three categories (GI, fatigue/weakness, dizziness), each scored 0-3. Total score 3+ with recent altitude gain = AMS. It is the official clinical diagnosis tool, not just "feeling bad."
How do I score myself on the trail?
Honestly, every evening — headache first (required for AMS), then GI symptoms (nausea, appetite loss), fatigue/weakness, and dizziness. Each 0-3. Score 3+ with headache after recent altitude gain = AMS = do not sleep higher until it resolves. Score partners too — self-reporting has a minimization bias.
What score means I have to descend?
Score 6+ with headache is moderate-to-severe AMS — descend, do not wait-and-see. Score 3-5 with headache is mild AMS — stop ascending, rest, treat symptoms, do not sleep higher until resolved. The score is a decision tool; when it says descend, descend.
Can I have AMS without a headache?
By the Lake Louise definition, no — headache is required for the AMS diagnosis. A high score without headache is probably something else (dehydration, exhaustion, GI bug). But altitude headache is the hallmark; at altitude, a headache plus other symptoms is AMS until proven otherwise.
Does the Lake Louise Score detect HAPE or HACE?
No — the score is for AMS only. HAPE (breathless at rest, gurgling, pink froth) and HACE (ataxia, confusion, irrational behavior) have separate, more serious criteria. A low Lake Louise score does not rule out the severe forms; those are different diagnoses entirely.
