Cronometer Micronutrient Guide UK: 10 Most Common GLP-1 Deficiencies

The 10 nutrients most commonly depleted in UK GLP-1 users, ranked by frequency, the symptoms each produces, and the dietary or supplement approach that fixes each. These aren’t theoretical risks — they’re the deficiencies that show up consistently in Cronometer data once users start logging honestly on a medication that reduces food volume by 40–60%. Knowing which 10 to watch means you can prevent most problems before they develop into symptoms.

Set up your tracking: Cronometer free →. Get personalised recommendations: free Lily & Loaf lifestyle analysis →

The 10 most common GLP-1 micronutrient deficiencies

Rank	Nutrient	UK RNI	Typical GLP-1 user intake	Key symptom
1	Protein	45–56g (minimum)	55–75g (vs 100–140g optimal)	Hair loss, muscle loss, fatigue
2	Magnesium	270–300mg	150–200mg	Poor sleep, cramps, constipation
3	Vitamin D	10mcg (400 IU)	3–5mcg	Fatigue, low mood, immune weakness
4	Iron (women)	14.8mg	7–10mg	Fatigue, breathlessness, hair loss
5	Vitamin B12	1.5mcg	0.8–1.2mcg	Brain fog, low energy, tingling
6	Fibre	30g	12–18g	Constipation, bloating
7	Zinc	7–9.5mg	4–6mg	Hair loss, taste changes, immunity
8	Omega-3 (EPA+DHA)	450mg EPA+DHA	100–200mg	Inflammation, dry skin, mood
9	Potassium	3,500mg	2,000–2,800mg	Muscle cramps, fatigue, palpitations
10	Calcium	700mg	500–600mg	Bone health (long-term), cramps

How to check each in Cronometer

Log 3–5 days of honest eating in Cronometer. On the diary view, click “Nutrition Report” to see all 84 nutrients against your targets. The ones shown in red or orange are below target. Focus on the top 10 above first — addressing these produces the largest improvement for most users.

Important: check the weekly average rather than any single day. Click “Trends” on any nutrient to see the 7-day average. One low day is noise; a consistently low weekly average is actionable.

The top 10 in detail

1. Protein

The most impactful gap on GLP-1 treatment. Every 10g of daily protein below your target increases muscle loss risk proportionally. Use the Protein Calculator UK for your exact target, then set it as a gram target in Cronometer (not percentage). Full guide: How to Get Enough Protein on GLP-1 UK.

2. Magnesium

70%+ of UK adults are already low; GLP-1 users drop further as food volume reduces. Magnesium glycinate is the best-absorbed form for sleep and anxiety. Magnesium citrate for constipation specifically. Target: 300–400mg daily from supplement if dietary sources are low. Lily & Loaf Triple Magnesium → Full guide: Magnesium on GLP-1 UK.

3. Vitamin D

UK adults average 3–5mcg dietary vitamin D against a 10mcg minimum RNI — and that’s before GLP-1 reduces food volume further. Blood test via GP is the most accurate indicator; supplement daily with 25mcg (1,000 IU) from October through April at minimum. Lily & Loaf D3+K2 →

4. Iron (particularly women)

Premenopausal women need 14.8mg daily — nearly double the male requirement — because of monthly blood loss. On GLP-1, red meat consumption typically drops. Result: ferritin (stored iron) depletes over 3–6 months. Ask your GP for a ferritin test; target ferritin above 50 ng/mL for optimal energy and hair health. Full guide: Iron on GLP-1 UK.

5. Vitamin B12

The slow-developing deficiency. Stores deplete over 6–12 months. Symptom onset is insidious — brain fog, low energy, mood changes that develop so gradually they’re attributed to other causes. Sublingual B12 (500–1000mcg) bypasses absorption issues. Full guide: B12 on GLP-1 UK.

6. Fibre

UK adults average 18g daily against a 30g target. On GLP-1 with 40–60% reduced food volume: typically 12–15g. Low fibre is the primary driver of the constipation that affects 30–40% of GLP-1 users. Fixes: chia seeds (10g per tablespoon), ground flaxseed, oats, lentils, beans. Full guide: Constipation on GLP-1 UK.

7. Zinc

Found primarily in red meat, shellfish, and pumpkin seeds. On GLP-1 with reduced meat consumption, zinc depletes at 3–6 months. Hair loss, taste changes, and slow wound healing are the characteristic cluster. See Zinc on GLP-1 UK. Target: 15mg elemental zinc daily from supplement if dietary sources are low.

8. Omega-3 (EPA+DHA)

Oily fish is the primary UK dietary source. On GLP-1, fish consumption often drops as rich foods become less appealing. Omega-3 at 2g+ EPA+DHA daily reduces inflammation, supports cardiovascular health, and improves dry skin — all relevant to GLP-1 users. Lily & Loaf Daily Balance Omega →

9. Potassium

Potassium is found in fruits, vegetables, beans, and dairy — all foods that are eaten less on a GLP-1 reduced appetite. Low potassium produces muscle cramps and in significant cases heart palpitations. Primarily addressable through diet: a banana + Greek yoghurt + handful of nuts provides approximately 1,000mg potassium. Electrolyte drinks help on injection days. See Electrolytes on GLP-1 UK.

10. Calcium

Calcium is the long-term concern — bone density loss from inadequate calcium compounds with GLP-1’s rapid weight loss effect on bone loading. Dairy is the primary UK source. On a GLP-1, dairy consumption (milk, yoghurt, cheese) typically reduces. Target: 700mg daily from food; supplement the shortfall. Particularly important for perimenopausal and postmenopausal women. See Mounjaro and Perimenopause UK.

The supplement stack that addresses the top 10

This is the evidence-based minimum supplement stack for most GLP-1 users, based on the deficiency data above:

Supplement	Addresses deficiencies	Product
Protein powder	#1 protein	Whey or pea protein
Magnesium glycinate	#2 magnesium	L&L Triple Magnesium
Vitamin D3+K2	#3 vitamin D	L&L D3+K2
Sublingual B12	#5 B12	Any sublingual cyanocobalamin
Omega-3 EPA+DHA	#8 omega-3	L&L Daily Balance Omega

Iron (#4) and zinc (#7) require testing before supplementing — over-supplementation carries risks. Check via GP blood test (ferritin for iron) and dietary intake in Cronometer before adding either.

For a personalised stack based on your specific symptoms rather than generic averages: take the free Lily & Loaf lifestyle analysis →

The knowledge layer

Understanding why these specific nutrients matter — the role of magnesium in GABA receptor activation, why B12 is required for myelin synthesis, the evolutionary reason humans needed dietary iron — converts supplement compliance from rule-following into genuine understanding. The audiobooks that cover this most accessibly: In Defence of Food (Pollan) and The Obesity Code (Fung). Start your free Audible trial →

Frequently asked questions

How do I check my micronutrients in Cronometer?

Log three to five days of eating, then open Nutrition Report from the diary view. The coloured bars show progress toward each target. Red = significantly below target; orange = moderately below; green = on track. Focus on anything red in the top 10 list above first.

Do I need to take all 10 supplements?

No — check Cronometer first. Many users are already adequate in several of these from diet. Address only the gaps your data shows, not a generic “GLP-1 supplement list.” The lifestyle analysis provides personalised guidance if you’d prefer a symptom-based recommendation.

Making the data actionable

The value of Cronometer’s micronutrient data is in how you act on it — not just in knowing the numbers. A practical protocol for using the top 10 deficiency list above:

Monthly review: at the start of each month, log 5 days of eating in Cronometer without changing anything about how you eat. Review the weekly averages for the top 10 nutrients above. Categorise each as red (below 70% of target), amber (70–90%), or green (90%+).

Action by colour: Red = prioritise addressing through diet or supplement. Amber = dietary improvement first; supplement if dietary change isn’t practical. Green = no action needed.

Supplement before testing for most: magnesium, vitamin D, and B12 are safe to supplement without testing (no upper-limit risk at standard supplement doses). Iron and zinc require testing before supplementing — over-supplementation carries risk. For the test-required nutrients, a GP blood test (ferritin for iron, serum zinc) provides the data Cronometer can’t.

The combination of Cronometer data (dietary gaps) and the free Lily & Loaf lifestyle analysis (symptom-based gaps) gives a complete picture — the Cronometer tells you what your diet is missing; the analysis tells you what your symptoms are signalling. Used together, they identify both dietary and functional gaps with high accuracy.

For the science behind why each of these specific nutrients matters in GLP-1 treatment: Audible’s free trial with In Defence of Food (Pollan) and The Obesity Code (Fung) provides the mechanistic understanding that makes the data meaningful.

Common questions about the top 10 deficiencies

How long does it take to correct a deficiency once I start supplementing?

It depends on which deficiency and how depleted stores are. Magnesium (for sleep): 2–4 weeks. Vitamin D (blood level): 3–4 months to raise significantly. B12 (if depleted): 4–8 weeks for neurological symptoms to improve, longer for full store replenishment. Iron (ferritin): 3–6 months with consistent supplementation. This timeline underlines why addressing these proactively (before symptoms develop) is more effective than corrective supplementation after significant depletion.

Should I test before supplementing or supplement and then test?

For the safe-to-supplement nutrients (magnesium, D3, B12, omega-3): supplement first, test later if symptoms persist. For test-before-supplementing nutrients (iron, zinc): test first, as over-supplementation carries specific risks. Your GP can order ferritin, serum B12, and vitamin D tests as a comprehensive GLP-1 nutritional screen at any standard blood test appointment.